Outdated composer install instructions

[theofidry]

The install instructions still refers to use the curl command, which has been removed in favour of the installer for various reasons.

What do you want to do? Update this page or just link to Composer install instructions?

[xabbuh]

I think we should remove the existing document from the table of contents. Then we should update all links to it to point to the installation instructions on getcomposer.org and only keep the existing one to maintain existing deep links from other third-party pages (we could update it to directly link to the subsections of the Composer installation documentation).

[wouterj]

We've written the article because the composer install docs still do not suggest a global installation by default. Unless that's fixed, we should keep the current doc imo.

[javiereguiluz]

I agree with Wouter.

[celdia]

We should keep this doc I think. Because we could need curl for others purposes or PHP projects.

[xabbuh]

@wouterj is right about the reason why we added the article in the past. So we should indeed update it.

[snoek09]

I'll update the instructions.