[Clean-up] Add a PRESUBMIT.py script for the proximity_auth component.

[Clean-up] Add a PRESUBMIT.py script for the proximity_auth component.

The script currently just verifies that all changes are "git cl format" clean.

BUG=none
TEST=none
R=tengs@chromium.org

Committed: https://crrev.com/97d21698eaee7cf0d4531f8b916f92374a733214
Cr-Commit-Position: refs/heads/master@{#297089}

[Tim Song, 2014-09-26 22:47:38]

lgtm

[Ilya Sherman, 2014-09-27 00:18:14]

The CQ bit was checked by isherman@chromium.org

[commit-bot: I haz the power, 2014-09-27 00:18:59]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/611673002/1

[commit-bot: I haz the power, 2014-09-27 01:17:53]

Committed patchset #1 (id:1) as b9bb5a26709dccb03329d22c3f7824bf1ead88ed

[commit-bot: I haz the power, 2014-09-27 01:18:28]

Patchset 1 (id:??) landed as
https://crrev.com/97d21698eaee7cf0d4531f8b916f92374a733214
Cr-Commit-Position: refs/heads/master@{#297089}