feat($repos): track repo name & owner instead of ID #3

...since these items are required for repo-specific API calls

- Removed repos route, since it is redundant

- Fixed bug in issues route caused by my incorrect assumption that the model function is called on a route every time it is activated.  The model function is only called on page reload.  It seems the setupController function is more appropriate.  Thanks to http://stackoverflow.com/questions/15678817/why-isnt-my-ember-js-route-model-being-called.