backend/textmate: Fixes for go1.3-ish map changes.

Previously (by chance!) the map[string] keys happened to be ordered
in the expected order, but this appears to not be a given with
go tip at the moment.

This change fixes the assumption of order by explicitly sorting
where order is important.
travis: Add rubex directory to PKG_CONFIG_PATH search directory.

As apparently libonig-dev doesn't contain a .pc file. Should fix
issue #263.
gofmt fixes
Add gofmt script for testing

If Go source code is checked into the repository but not properly
formatted using gofmt, this new script will print the aberrant files and
exit 1 to fail Travis tests.

It's listed as a new script in .travis.yml. All scripts are run (even if
any of them exit nonzero), so regular tests still occur if the gofmt
check fails.

The script also ignores the 3rdparty directory, since that contains git
submodules (some of which have unformatted Go code in them). Since those
repositories are not under our control, we don't want to check them for
formatting.