tests: Use libcangjie_cli arguments

Now we can, thanks to @yookoala
tests: Move inheritance a bit

There's no reason to make each of our test cases a mixin, making our
BaseTestCase inherit from unittest.TestCase simplifies writing new unit
tests.
tests: Test **all** filters on

Thanks to @yookoala's work, we can do that now, which makes for better
coverage of the libcangjie data.
tests: Check Cangjie version 5 too!
Merge pull request #23 from Cangjians/tests

Various unit test improvements