Renamed generated branch file from branch+extension to branch.gen+extension
Added importFormat in options
Added encoding in options
Added csslinting during tests to assert that generated css files are compliant
Moved csstree.js in lib/
Simplify the use of the file csstree
Moved ./task/lib -> ./lib
Renamed csstree.build -> csstree.model
Delete Tree.depth, wasn't used
Added comments