Require ‘gocode’ via TextMate 2’s required command system

This leads to a better user experience and allow the user to set TM_GOCODE instead of updating PATH.
Change (advanced) completion command’s key equivalent to ⌥⎋

Previously this command eclipsed the simple buffer completion, of which it is not a superset, so we should keep both actions around, especially since this command does not work before the user has installed ‘gocode’.
Implementation tweaks

Ask TextMate to “save modified files” and use TextMate.save_if_untitled in the command, which will create a temporary file for untitled documents. The advantage is that whenever there is a file, TextMate will handle saving it, rather than delegate this to the command.

Limit TextMate.make_project_master_current_document and the ‘:use_hashbang’ argument to the commands that call TextMate.executor. The method will check if the user has setup a different master file, and if so, change TM_FILEPATH to point to the master file, which isn’t relevant for Run (⌘R) and documentation lookups. Likewise, the ‘:use_hashbang’ argument is only relevant for TextMate.executor.

The ‘:interactive_input’ argument is no longer supported and has been removed.
Enable auto-scroll for command output (run/compile/test)
Do not scope whitespace as a variable

Previously we would scope a declaration like ‘var x int = 0’ as ‘variable.other.go’ which would treat it as a single word for word movement, selection, buffer completion, and similar functionality.
Exclude whitespace in function declarations from variable scope

This improves word movement, though ideally we would match the content correctly, as we presently do scope asterisk, braces, and similar, as variable, not to mention that only part of the content is actually variables, the rest are type info.
Merge branch 'master' of git://github.com/sorbits/go.tmbundle into sorbits-master

* 'master' of git://github.com/sorbits/go.tmbundle:
  Exclude whitespace in function declarations from variable scope
  Do not scope whitespace as a variable
  Enable auto-scroll for command output (run/compile/test)
  Implementation tweaks
  Change (advanced) completion command’s key equivalent to ⌥⎋
  Require ‘gocode’ via TextMate 2’s required command system