Split webathena.js into core piece and UI piece

Easier to unit test the non-UI bits when they don't have the equivalent
of a main function.
Add unit tests

For now just import the test vectors for nFold. Issue #27. Export
kcrypto.nFold for testing. We should look into not having to do that.
mit_des_string_to_key tests

Issue #27.
Test mod-crc-32

Also unexport mit_des_string_to_key. We didn't need to. Issue #27.
Add PBKDF2 test vectors

Seems we actually fail a case. Issue #27.