ci: Build against the 1.x branch of libcangjie and pycangjie

libcangjie master broke its API, so we can't build the 1.x branch of
ibus-cangjie against libcangjie/pycangjie master any more.

This is all perfectly expected though, but we need to tell Travis
about it.
tests: Use the memory GSettings backend

Without this, the tests will interfere with the environment they are ran
it.