Experiment closure compiler - should trigger errors

local compiler.jar
should trigger errors on Travis
Fix typo + plugin compile step in Travis
Plug 'compile' on test

Let's break all the thingz !
Closure Compiler: Fix All The things !

 - Adding some small fixes to pass compile step (mostly /** instead of
/*).
  - Adding some closure externs
Show closure compiler warnings

 - Flush JS binary to temporary file instead of STDOUT
 - Flushing to temp file allow display of warnings (mostly our fake
require/provide)
 - gitignore the temp JS file
 - Clean some comments
Merge pull request #127 from juliandescottes/closurecompiler

Basic wiring of Closure compiler
Merge branch 'master' into feature-gif-export-panel
Dev environment : closure compiler + jshint update

Fixed error raised by closure compiler
Added es3 option to jshint (detect trailing commas)
Added curly option to jshint (missing curly braces for if/for blocks)
Removed trailing whitespaces (not enforced through jshint though)