feat(directive): require and advanced options

add "require" array for specifying ace.require loads, and add "advanced" object in the directive options for specifying unlisted ace options. This is done to try and make customizing the editor more robust from the directive alone, and possibly eliminate the need for controller code related to the editor.
Merge pull request #60 from ciel/feat-ace-add-require-and-advanced-option

feat(directive): require and advanced options