Merge two fixes and change look of plugin

Fixed issues:
* To <blank> shows up when MBTA returns weird data - https://github.com/wolfd/MBTAShortcoder/issues/3 
* -0 sometimes displays - https://github.com/wolfd/MBTAShortcoder/issues/1

Changed look of plugin.
![image](https://cloud.githubusercontent.com/assets/930169/2760594/fa893b9a-c9ba-11e3-8ae8-f96db48cfadf.png)