Add "Line Based" support

- [x] Add keycaps for "Line Based" runs
- [x] Add menus for "Line Based" runs
  - Right/`ctrl` clicking the line number will provide a menu option to run at the current line.
- [x] Update grammars.coffee for "Line Based" runs

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![line-based](https://cloud.githubusercontent.com/assets/1694055/2765666/ee848090-ca26-11e3-98e0-405e80d53609.gif)