Completed task: "Number of Issues Closed Per Contributor".

This pull request addresses the following issues:

* #49: Create server route for querying number of issues closed per contributor
* #50: Parse number of issues closed per contributor data before sending to client
* #51: Create controller for handling number of issues closed per contributor data on client
* #52: Create factory for getting number of issues closed per contributor data on client from server
* #53: Create partial for displaying number of issues closed per contributor on client

The number of issues closed per contributor page is located at `/#/issues_closed` URL in the browser which hooks to the  /api/issues_closed  endpoint on the server. User must specify the exact repository owner and repository name (case insensitive) before the page displays the number of issues closed per contributor for the repository.

Although, this pull request completes the specified task, it is a temporary implementation to the desired goal. See issue #69 for details.