Use Hyper+<key> to launch various apps

KeyRemap4MacBook 8.1 added the ability to define key mappings that will
launch specific apps [1]. Let's put that to good use.

  - Declare dependency on newer verion of KeyRemap4MacBook.
    (Technically we only need 8.1, but let's use the latest stable
    version: 8.3.)
  - Add optional key mappings for launching apps:
    - Right Option + B to open Chrome ("B" for "Browser")
    - Right Option + C to open PropanePlus ("C" for "Chat")
    - Right Option + E to open Submlime Text ("E" for "Editor")
    - Right Option + G to open Mailplane ("G" for "Gmail")
    - Right Option + R to open Rdio ("R" for "Rdio")
    - Right Option + T to open iTerm ("T" for "Terminal")

[1]: https://pqrs.org/macosx/keyremap4macbook/history.html.en