Get info about new repositories from github when they are added.

[bethgrace5]

*in RepositoryAction.addRepository() check if the repository exists on github, and get the name, issues, and milestones associated with it.
*When adding a repository that is not in the database, or does not exist on github, display message indicating repository could not be found.

[bethgrace5]

the name and full_name are retrieved from github, but issues and milestones are not at this point.