Feat/slide out menu/main

- Main weather view now slides over to reveal a table which contains names of locations.
- Selecting one of these locations reloads the weather for that location.
- Implemented using [ECSlidingViewController](https://github.com/ECSlidingViewController/ECSlidingViewController) pod
- Only works for mock service at this point

If you're interested @rburr @lukesteffen @blakecarrier