Don't track .DS_Store or temp (~) files

Change-Id: I8d0e59a27c2dfb98079996f04383ae160df27391
Reviewed-on: http://review.couchbase.org/43155
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: thomas anderson <thomas.couchbase@gmail.com>
Tested-by: thomas anderson <thomas.couchbase@gmail.com>