.travis.yml: Build all branches, except wip ones

Restricting tested branches to master branches and merge/ branches was
far too strict. Instead of doing that, skip wip branches only, and test
everything else.

Signed-off-by: Gergely Nagy <algernon@balabit.hu>
.travis.yml: Enable VERBOSE mode when testing

We want to see the test failures when they happen in CI, so enable
VERBOSE=1 when doing make check and make func-test.

Signed-off-by: Gergely Nagy <algernon@balabit.hu>