Update to use grunt 0.4.x

Change directives code to grunt template syntax. Register new grunt modules
as tasks. Update default and minify task to use updated tasks. Add grunt
modules to package.json.

Remember to switch from grunt 0.3 to grunt 0.4 use:
$ npm uninstall -g grunt
$ npm install -g grunt-cli
$ npm install # from webinos dir to install new grunt deps

Jira-issue: WP-779
New task to wrap concatenated code

Add new wrap task since grunt 0.4 currently doesn't support adding a footer
to concatenated code. Revert this commit in case footer support comes back
to grunt.

Jira-issue: WP-779
Add jshint task

Task which runs all JavaScript files through jshint for linting.

Jira-issue: WP-779