Stubbing global objects' methods

• Add stubs to mock global objects methods

var $ = require('jquery'),
    stubbed = this.generateStub($, "ajax"),
    object = {
        method: function() {
            $.ajax("http://foo.bar");
        }
    };

this
    .if(object.method())
    .then()
        .stub(stubbed).wasCalled().withArguments("http://foo.bar")
;

$.load.restore();

• Stubbed methods are restored after each test
• Add Grunt Task
• Fix exit status code