Introduce FormatNegotiatorInterface, add PHPDoc
Add test to cover a condition in LanguageNegotiator
Add more tests, fix getFormat() for specific media types

+ fix README
Merge pull request #19 from willdurand/new-interface

Add FormatNegotiatorInterface
Extract priorities matching

LanguageNegotiator now matches plain language

Fix #17
Merge with origin
Made priority matching return item from priorities in favor of headers from user agent