Update .gitignore file
Update .gitignore file

Added the following files/folders to ignore

*~
*.DS_Store
build

Change-Id: I0f12cd44b7cfaa5153767a8d0a183c891560b262
Reviewed-on: http://review.couchbase.org/49824
Reviewed-by: thomas anderson <faa2c0189873991686fbb8a0db4c162f340af90c@yahoo.com>
Tested-by: thomas anderson <faa2c0189873991686fbb8a0db4c162f340af90c@yahoo.com>

mikewied/cbagent,couchbase/cbagent,vmx/cbagent