src/MxList.hs: explicit imports/exports.
src/MxList.hs: use implicit Typeable derivation.
src/MxList.hs: use an explicit export list.
Add a doctest test suite. Add docs and rc file example for --exclude-mx. Update docs for some functions. Split a few local functions into global ones for testing. Add doctests for existing global functions.
Initial commit of something working.