remove turbolinks
create rails 4 concerns from helpers

- move GithubHelper to a concern
- move RepositoryHelper into a concern
- create a `#fetch_gh_repo` method in GithubHelper
- move local git methods into GithubHelper
- remove duplicate `require 'json'`
use new `#fetch_gh_repo` method
fix mc
Merge pull request #82 from alexung/concerns

REVIEW BEFORE MERGE: Concerns Refactor