Add `full-fit-in` feature
Similiar to `fit-in`, while scaling the image to exactly fill a given box to the full without cropping
Thumbor support for gif and animated gif images.
travis gifsicle requirement
removing commented code
Removed finding gifsicle every request. Now if the configuration is made and the server can't find gifsicle the server won't go up
Merge branch 'master' into fit-full
fix style
Merge pull request #321 from thumbor/gifsicle

Thumbor support for gif and animated gif images.
Release 4.2.0
Merge pull request #322 from moeffju/fit-full

Add `full-fit-in` feature
removing useless whitespace