.travis.yml: Test the merge/ prefixed branches on Travis CI too

Signed-off-by: Gergely Nagy <algernon@balabit.hu>
Bump the @version pragmas to 3.6

Since the default version was switched to 3.6 earlier, bump the @version
of the default config and the in the func-tests too.

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