Improving gitignore
Adding add_error_fun/2
sync_push now returns a list of success/error tuples
Fixed a compiler warning.

Headers on src/gcm.erl line 170 was unused, prefixed with an _ and turned on warnings_as_errors
change travis-ci to test on erlang 16B 1-3 and 17
Merge pull request #7 from zkessin/travis-versions

Travis versions
Fixing test
Removing test
Merge pull request #5 from StephanDollberg/return_from_sync_push

sync_push now returns a list of success/error tuples
Updated from upstream: conflicts resolved