Added API calls, a dish page, and other cleanup

- Added an API util. The API util uses a combination of Volley and Gson to provide efficient and asynchronous api calls. Right now the only API is to get a list of dishes but adding more is trivial.

- Moved the list of dishes to its own fragment. It starts by default when `MainActivity` launches. It should be replaced by a home fragment when the search ui is completed (@kousun12). The fragment uses the new `ApiUtils`

- Added a dish view for individual dishes based on the mocks by @ktzhu. It currently loads the images, shows the edit button (although it does nothing), dish name, and restaurant name but doesn't show comments. It can be accessed by clicking a dish in the dish list.

- Fixed a bug that caused a new `BitmapLruCache` to be created for every dish instead of reusing the same one.

- Lightened up the menu icon

- Replaced the drawer with a `ListView` in anticipation of it actually being used for something.