Add jUnit reporting

Added Junit support,
1/ moved out some formatting specific outside from task/qunit.js : formatters/grunt.js
2/ improved formatter to listen to qunit.junit event and catch about url changes : formatters/grunt.js
3/ added new task option : junitDir
4/ added a new bridge to embed junit out of the box : phantomjs/junit-bridge.js
6/ update doc / package version

Notes : The junit-qunit dependence is thatone : https://github.com/jquery/qunit-reporter-junit

BTW/ fixed the docs/qunit-options.md : missing console option

The tests passes correctly here.
JSHint passes too.

Hope it could get merged into the trunk.