Replace calls to deprecated link_to_function with doc-ready functions.

Created by: robbkidd

Rails 3.2.4 deprecated the link_to_function helper method. rails/rails@9dc57fe9c

It appears there are no tests for the original link_to_function behaviors. I tested these changed manually by running a GitLab instance in development mode, adding a project for the current GitLabHQ code base and creating a merge request with a branch with more than 8 commits.

However, I found it difficult to create the correct state in a view spec or request spec to test the old and new code. Any ideas where and how I could add tests for this? Maybe in the new cucumber tests? I believe it is a matter of having the test gitlab repo--tmp/tests/gitlabhq--have some branches and commits in the expected states. Does that seem right?