improve templates (#189)

* improve templates
* fix filenames and extend contributing

Author: OriolAbril

.github/ISSUE_TEMPLATE/bug-report.md

@@ -1,5 +1,22 @@
 ---
-name: 'Bug Report'
-about: Inform about errors and mistakes in the notebooks
+name: 'Notebook Error Report'
+about: Inform about errors and mistakes in the example notebooks
 
 ---
+
+**Notebook title**:
+**Notebook url**:
+
+## Issue description
+Explain the bug, error or mistake, where it is in the notebook, if it happens
+only once or multiple times...
+
+*Note that this issue tracker is about the contents in the notebooks, if
+the notebook is instead triggering a bug or error in pymc3, please
+report to https://github.com/pymc-devs/pymc3/issues instead*
+
+## Expected output
+If applicable, describe what should happen instead.
+
+## Proposed solution
+If applicable, explain possible solutions and workarounds.

.github/ISSUE_TEMPLATE/config.yml

@@ -0,0 +1,8 @@
+blank_issues_enabled: false
+contact_links:
+  - name: PyMC Discourse
+    url: https://discourse.pymc.io/
+    about: Ask usage questions about PyMC3 or doubts about the examples here
+  - name: PyMC3 bug report
+    url: https://github.com/pymc-devs/pymc3/issues
+    about: Please report bugs or propose enhancements of the PyMC3 library here.

.github/ISSUE_TEMPLATE/notebook-proposal.md

@@ -0,0 +1,20 @@
+---
+name: 'Propose a new example notebook'
+about: Propose new content based on gaps in the current collection
+labels: proposal
+
+---
+
+# Notebook proposal
+**Title**: Use this also as issue title
+
+## Why should this notebook be added to pymc-examples?
+Explain why this topic is interesting and useful to PyMC3 users.
+
+## Related notebooks
+Cover related notebooks on which this notebook will build,
+make sure that the notebook is not duplicated and
+explain whether it should be a new notebook or extend an existing one.
+
+# References
+If applicable, references and material that could help in writing the notebook.

.github/ISSUE_TEMPLATE/tracker.md

@@ -1,6 +1,6 @@
 ---
 name: 'Tracker issue'
-about: Create a tracker issue for the GitHub project
+about: *Internal template for PyMC documentation team only*
 labels: tracker id
 
 ---

CONTRIBUTING.md

@@ -95,6 +95,8 @@ We recommended that your contribution complies with the following guidelines bef
 
 *  Use the pull request title to describe the issue and mention the issue number in the pull request description. This will make sure a link back to the original issue is created. For example, use `Use ArviZ in sampler stats notebook` as a title and link to [#46](https://github.com/pymc-devs/pymc-examples/issues/46) in the description.
    * Please do not submit PRs that are not addressing an issue already present in the issue tracker.
+   * If you want to add a new notebook and no issue related to it is present yet, open one so we can
+     discuss the best way to add the content to the repo. We have an issue template for that.
 
 *  Prefix the title of incomplete contributions with `[WIP]` (to indicate a work in progress). WIPs may be useful to (1) indicate you are working on something to avoid duplicated work, (2) request broad review of functionality or API, or (3) seek collaborators.