Added filter for Dart
In LessphpFilter, allow formatter to be changed.
In LessphpFilter, allow comments to be preserved in the output.
Add tests for LessphpFilter's 'formatter'.

https://github.com/amyboyd/assetic/commit/180c7dbe3b1a1a78348188682b76cf3d479f5320
Add tests for LessphpFilter's 'preserve comments'.

https://github.com/amyboyd/assetic/commit/3351d6386be3452e7529a3dc477784da8688a3d6
fixed PHP notice in CssRewriteFilter

fixes #311
fixes #327
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'pierredup/master'
updated DartFilter and test

 * use BaseProcessFilter
 * cleanup output file
 * smarter test setup
implemented base filter and test case classes

made tests smarter
added travis image
fixed formatting
cleaned up travis config
have travis install more deps
fixed assertion in php 5.4
Adding option for setting java stack size

With some css files, yuicompressor generates a stack overflow exception.
Here I add an option for setting java stack size
cleaned up last commit
added composer self-update
added missing license block
updated license years