travis: Fix TRAVIS_GO_VERSION handling (again)
travis: Fix TRAVIS_GO_VERSION handling (again)

This change effectively reverts the previous
e51f7f600b3251133c77d1c9789b6ab3bacf3d0f commit.
TRAVIS_GO_VERSION *is* confusingly `1.8` (no patch revision) for some
go versions and `1.8.3` (with patch revision) for other go versions.

This change restores the previous regex pattern match, improving it to
also deal with the no-patch-revision case.

anguslees/sealed-secrets