Support Grunt 0.4.x

- Rename grunt.js file to Gruntfile.coffee
- Use grunt.helper with legacyhelper library.
- Fix banner option (<banner:banner> options was removed from grunt 0.4)
- Use grunt.file.readJSON to parse JSON.
Refactor jshint usage, extract options into .jshintrc file, still doesn't actually lint a single file
Replace concat-helper with proper banner option
Release 0.4.0 for grunt 0.4 compability, update readme
Move jshint to devDependencies
0.4.1
Switch to clean-css (same as grunt-contrib-mincss uses) and exposes their options
Release 0.5.0, after switch to clean-css
Use log.ok [x files lint free.] for consistency with jshint task
0.5.1
Grunt 0.4rc5 compat
0.5.2
Grunt 0.4rc5 compability for cssmin task
0.5.3