Add support for VersionEye dependency tracking

[DaSourcerer]

This pr adds support for the VersionEye dependency tracking service. It'll show as a button in the readme quite similar to Travis CI. VersionEye builds dependency graphs via found composer.json files in this very case, so no further steps are required on the side of Yii devs.

[suralc]

Once there is decent code coverage, it might be interesting to have this for feature pull-requests:

https://coveralls.io/info/features

On the pr:
Does it work correctly? As we have muotiple composer.json files in the same repo 2hich are reffering to each other. Would make more sense to place it on the readme in /framework and refer to the yii2-framework repo amd not the main. And do the same for extensions.

[DaSourcerer]

Once there is decent code coverage, it might be interesting to have this for feature pull-requests:
https://coveralls.io/info/features

Hm, interesting. For future reference: There is a way to integrate this in Travis CI.

Does it work correctly? As we have muotiple composer.json files in the same repo 2hich are reffering to each other.

Yes, it does. Although VE has GitHub integration, it seems to prefer the informations it finds over at packagist.org.

Would make more sense to place it on the readme in /framework and refer to the yii2-framework repo amd not the main.

I beg to differ. This button is for the framework dependencies. So it makes sense to place it where visibility is the highest (which happens to be the main README.md). However, there would be nothing against adding buttons to the other readmes. As I see it, VersionEye has them already tracked.

[qiangxue]

Thanks!

[suralc]

Coveralls support would look simliar to this: (implemented it in a branch on my fork)

I'll open a pull-request with travis-conf and phpunit.xml.dist changes, if this is considered useful.

Pull-request:

https://github.com/suralc/yii2/pull/1

Overview:

https://coveralls.io/r/suralc/yii2

Job Overview:

File List Overview:

File-Overview:

[samdark]

Coveralls definitely looks useful. For 1.1 as well.