Added Bitly url shortener.
Merge pull request #6 from shouze/feature/bitly-shortener

Added Bitly url shortener.
Define some exceptions when provider fail.
Add property access dependency.
Merge pull request #8 from stephpy/exceptions

Define some exceptions when provider fail.
Add curl http adapter
Merge pull request #7 from stephpy/curl

Add curl http adapter
Be BC with 2.* of symfony/property-accessor