Feature: Always start git commit messages with cursor in the upper left

Previously, git commit messages would start wherever the cursor left off of the
previous git commit message which made no sense.  99% of the time, the next time
you edit that file, you want to be in the first row, first column.

By adding an additional command to the auto command for files named
`COMMIT_EDITMSG`, we override the position of the cursor to be in the upper
left.

--------------------------------------------------------------------------------
Change-Id:     I186b6018eee8719aa3ddfba15c4a0934b17b601f
Signed-off-by: Jeff Felchner <accounts+git@thekompanee.com>