Single tap graph bar for toast-like information display

Closes #30 
Fixes #34 

Show a details "toast" like UI element when someone taps a bar in the graph in stats.  This should be similar to the data presented in the mouse over on web stats.  This is ultimately a temporary solution until the API fully supports us doing a details page like when a bar is clicked on the web.

Both code and UI is up for review.

cc: @isaackeyet @drw158 @daniloercoli 

![ios simulator screen shot jul 23 2014 11 44 53 am](https://cloud.githubusercontent.com/assets/373903/3676447/b590ef76-1288-11e4-85cd-d0fc6f03ab6a.png)