Big refactor.

- Hunk stage/undo/preview no longer saves the buffer.
- Hunk undo no longer makes locations go out of sync.
- Grep can be opted out of (grep output with ansi escapes is number one cause
  of issues).
- Replaced g:gitgutter_grep_command with g:gitgutter_grep.
- Always runs git-diff the same way instead of in two possible ways.
- Separated detection of git tracking from diffing.
- Simplified path handling.
- Removed support for xolox shell: Windows taskbar does not flash with async
  jobs.
- Removed g:gitgutter_{eager,realtime}.
- Simplified implementation generally.

doc/gitgutter.txt

@@ -22,11 +22,11 @@ CONTENTS                                                    *GitGutterContents*
 1. INTRODUCTION                                         *GitGutterIntroduction*
                                                                     *GitGutter*
 
-Vim Git Gutter is a Vim plugin which shows a git diff in the 'gutter' (sign
+GitGutter is a Vim plugin which shows a git diff in the 'gutter' (sign
 column). It shows whether each line has been added, modified, and where lines
 have been removed.
 
-This is a port of the Git Gutter plugin for Sublime Text 2.
+This is a port of the GitGutter plugin for Sublime Text 2.
 
 ===============================================================================
 2. INSTALLATION                                         *GitGutterInstallation*
@@ -301,20 +301,6 @@ Add to your |vimrc|
   let g:gitgutter_highlight_lines = 1
 <
 
-TO STOP VIM-GITGUTTER RUNNING IN REALTIME
-
-Add to your |vimrc|
->
-  let g:gitgutter_realtime = 0
-<
-
-TO STOP VIM-GITGUTTER RUNNING EAGERLY
-
-Add to your |vimrc|
->
-  let g:gitgutter_eager = 0
-<
-
 TO TURN OFF ASYNCHRONOUS UPDATES
 
 By default diffs are run asynchronously.  To run diffs synchronously