Add an init method on Proxy

To avoid bad behavior on consecutive calls
Merge pull request #18 from j0k3r/proxy-init

Add an init method on Proxy
Fix wrong place to reset content & url
Fix some alerts from Insight

https://insight.sensiolabs.com/projects/b3688b01-a0db-4325-a8ba-dcc59ab00fe4/analyses/36
Fix annotation
Fix test on wrong http method
Merge pull request #19 from j0k3r/insight

Cleanup from Insight
Cleanup
Fix typo
Rename Parser to Improver

And use the Symfony2 chain logic instead of custom (ugly) one
Cleanup