Readme update for clarity

I thought the readme might be better organized to clarify the difference
between frontend and backend.

Alongside various stylistic changes, I've done my best to group frontend
and backend related comments together.

Author: charlieegan3

README.md

@@ -1,62 +1,79 @@
 # crates.io
 
-Source code for the default registry for Cargo users. Can be found online at
-[crates.io][crates-io]
+Source code for the default [Cargo](http://doc.crates.io) registry. Viewable 
+online at [crates.io](https://crates.io).
 
-[crates-io]: https://crates.io
+This project is built on ember-cli and cargo, visit
+[iamstef.net/ember-cli](http://ember-cli.com/) or
+[doc.crates.io](http://doc.crates.io/) respectively for more information.
 
-## Development Setup
+## Working on the Frontend
 
-* `git clone` this repository
-* `npm install`
-* `npm install -g ember-cli`
-* `npm install -g bower && bower install`
-
-## Making UI tweaks or changes
+```
+git clone https://github.com/rust-lang/crates.io.git
+cd crates.io/
+npm install
+npm install -g ember-cli bower
+bower install
+```
 
-This website is built using [Ember.js](http://emberjs.com/) for the frontend,
-which enables tweaking the UI of the site without actually having the server
-running locally. To get up and running with just the UI, run:
+The website's frontend is built with [Ember.js](http://emberjs.com/). This 
+makes it possible to work on the frontend without running a local backend.
+To start the frontend run:
 
-```
+```bash
 npm run start:staging
 ```
 
-This will give you a local server to browse while using the staging backend
-(hosted on heroku at https://staging-crates-io.herokuapp.com).
+This will run a local frontend using the staging backend (hosted on Heroku at 
+[staging-crates-io.herokuapp.com](https://staging-crates-io.herokuapp.com)).
 
-If you'd like to run the server with a specific different backend, you can specify specific arguments to `npm start`. For example you can set the proxy to `https://crates.io/` to use the live instance, but do be aware that any modifications made here will be permanent! To do this, run:
+If you'd like to run the frontend with a specific backend endpoint, you can 
+specify arguments to `npm start`. For example you can set the proxy to 
+`https://crates.io/` to use the production version. 
 
-```
+**Note: it is also possible to make changes to the production data**
+
+To do this, run:
+
+```bash
 npm start -- --proxy https://crates.io
+# or
+npm run start:live
 ```
 
-The same is also available as:
+**Note**: This requires npm 2.
+
+### Running Tests
+
+Install [phantomjs](http://phantomjs.org/), typically: `npm install 
+phantomjs-prebuilt`.
+
+Then run the tests with:
 
 ```
-npm run start:live
+ember test
+ember test --server
 ```
 
-This requires NPM 2.0.
+## Working on the Backend
 
-## Working on the backend
-
-If you'd like to change the API server (the Rust backend), then the setup is a
-little more complicated.
+After cloning the repo, steps for setting up the backend API server are as 
+follows:
 
 1. Copy the `.env.sample` file to `.env` and change any applicable values as
     directed by the comments in the file. Make sure the values in your new
     `.env` are exported in the shell you use for the following commands.
 
-2. Set up the git index
+2. Set up the git index:
 
     ```
     ./script/init-local-index.sh
     ```
 
     But *do not* modify your `~/.cargo/config` yet. Do that after step 3.
 
-3. Build the server.
+3. Build the server:
 
     ```
     cargo build
@@ -65,23 +82,25 @@ little more complicated.
     On OS X 10.11, you will need to install the openssl headers first, and tell
     cargo where to find them. See https://github.com/sfackler/rust-openssl#osx.
 
-4. Run the migrations
+4. Run the migrations:
 
     ```
     ./target/debug/migrate
     ```
 
-5. Run the servers
+5. Start the backend server:
 
     ```
-    # In one window, run the api server
     ./target/debug/server
+    ```
+
+6. **Optionally** start a local frontend:
 
-    # In another window run the ember-cli server
+    ```
     npm run start:local
     ```
 
-## Running Tests
+### Running Tests
 
 1. Configure the location of the test database. Note that this should just be a
    blank database, the test harness will ensure that migrations are run.
@@ -99,30 +118,13 @@ little more complicated.
     export S3_BUCKET=alexcrichton-test
     ```
 
-3. Run the API server tests
+3. Run the backend API server tests:
 
     ```
     cargo test
     ```
 
-4. Install [phantomjs](http://phantomjs.org/)
-
-5. Run frontend tests
-
-    ```
-    ember test
-    ember test --server
-    ```
-
-## Tools
-
-For more information on using ember-cli, visit
-[http://iamstef.net/ember-cli/](http://ember-cli.com/).
-
-For more information on using cargo, visit
-[doc.crates.io](http://doc.crates.io/).
-
-## Deploying a Mirror
+## Deploying & Using a Mirror
 
 **DISCLAIMER: The process of setting up a mirror is a work-in-progress and is
 likely to change. It is not currently recommended for mission-critical
@@ -156,7 +158,7 @@ The only config variable you need to set is `GIT_REPO_URL`, which should be the
 git URL of your crates index repository; see the next section for setup
 instructions for that.
 
-### Index mirror setup
+### Index Mirror Setup
 
 You also need a mirror of the crates.io git index, and your index needs to point
 to your API server.
@@ -178,7 +180,7 @@ to your API server.
     official index. How to do this depends on how you are hosting your index,
     but could be done through `cron` or a scheduled CI job, for example.
 
-### Cargo setup
+### Local Cargo Setup
 
 **NOTE: The following configuration requires a cargo version newer than
 0.13.0-nightly (f09ef68 2016-08-02). The version of cargo that comes with rust