Test cases

A set of test cases, for #27.  ~~This is **not ready for merging** yet, but I'm opening it anyway, for early review.~~

# State

- [x] Makefile target
- [x] Travis CI setup
- [x] Tests for major mode settings
- [x] Tests for alignment
- [x] Tests for imenu
- [x] Font lock tests

I'd postpone indentation tests until after SMIE, because right now, we'll be testing broken and partly dysfunctional code anyway.