Allow specifying controller with absolute path

[lalau]

The current code only allow relative controller path but in some cases we want to have a centralized location where test codes can share controllers locally. Arrow should support setting controller from absolute path. The path resolution is done by path.resolve: http://nodejs.org/api/path.html#path_path_resolve_from_to

[travisbot]

This pull request passes (merged 1c57820f into 66b2c44b).

[proverma]

Thanks Lawrence.