UI fixes to debugger

- mouse-1 pushes buttons
- Show the debugger-output buffer on output
- make faces and fringes consistent with gud.el
Merge pull request #53 from edani/debug-218

UI fixes to debugger
added more sbt keybindings #488
added supporting funcitons in sbt-mode.el
Merge pull request #54 from slipset/more-sbt-keybindings

added more sbt keybindings #488
Print error for string under point https://github.com/ensime/ensime-server/issues/638
Added keybinding
Merge pull request #55 from slipset/warning-under-point

Display warning for string under point #638