make sure we add go to the front of choosen go versions
update gvm on each run for now
add a special rule for gvm install tip
Rework go version alias handling

such that `tip` still passes through, but numbered versions are prefixed
with `go`.  Also aliasing '1.0' to '1.0.3'.
Merge pull request #111 from modcloth-labs/special-case-go-number-versions

Rework go version alias handling
Merge remote-tracking branch 'upstream/master' into go-installs-with-go-install

Conflicts:
	lib/travis/build/script/go.rb