Test mei encoding

[MrMondrian]

Resolves: (#ID-of-the-issue)

• I passed the docker hub test, and images can be built successfully.
• I passed the GitHub CI test, so rodan functionalities and jobs work.

Adds state machine based test file for mei encoding.

FIRST TEST CASE: Syllables well formed

• elements that should be outside syllable are outside syllable
• elements that should be inside syllable are inside syllable
• elements that can be either are in only after a neume is in

SECOND TEST CASE: zones and facsimile are a bijection

THIRD TEST CASE: Proceeds and follows

• Every syllable has a syl XOR a follows
• Every syllable with a proceeds has a follows immediately after
• Every syllable with a follows has a proceeds immediately before

FOURTH TEST CASE: All bounding box coordinates are non-negative

[timothydereuse]

looks good - i think the state machine was the right way to go for testing, it looks a lot more robust than what I was doing back in the day with libMEI.

still wish the build_mei file wasn't nearly a thousand lines long but I think it kinda has to be, so that's a good enough place to leave it.