Support loading lyrics from midi

[oxygen-dioxide]

Midi files can contain lyrics. Many music creation softwares that deal with lyrics, especially sheet music editor and singing voice synthesizers, such as Musescore and OpenUtau, can create midi file with lyrics. After this PR, we can load lyrics from midi files.

#356 will be solved.

[coveralls]

coverage: 93.013% (+0.001%) from 93.012%
when pulling 032c51f on oxygen-dioxide:midilyrics
into 41b6b6f on cuthbertLab:master.

[mscuthbert]

hi @oxygen-dioxide -- can you add tests including doctests for getLyricsFromEvents. Thanks.

[oxygen-dioxide]

Added tests for lyrics importing. The song for testing is a small part of Haydn's String Quartet Op. 76 with Chinese and Korean lyrics.
Different softwares use different encoding when writing midi file, and some of them use your system encoding. Music21's parser uses UTF-8 encoding by default. To specify encoding, use converter.parse(fp, encoding_type = encoding). Tests for UTF-8, GBK and EUC-KR encodings are added.

[mscuthbert]

Almost there -- can you fix the errors in flake8 run:

flake8 music21

fixing those should fix the pylint also.

Because note is a module name we don't use it as a variable name (same w/ pitch, interval, etc.) so use n or n1 etc.

[oxygen-dioxide]

I also want to implement "- to Slur". In singing synthesis softwares, we use - to make the current note and the previous note a slur, which means the syllable sings across two notes. So I think we should parse midi lyric - as Slurs in music21.
Example:

[mscuthbert]

Closing and Reopening to get a clean slate.

[mscuthbert]

Hi @oxygen-dioxide -- Great PR -- there are still a few changes I wanted to make but they were easier for me to do because they mostly touched on parts of the system that were pre-existing.

As far as "-" getting translated to slurs automatically, I'm not going to put that into the music21 MIDI parsing routines unless it becomes a standard (or de-facto standard) across all of MIDI. I'd be glad to put example code of how to do this after the fact somewhere in the documentation system. Glad to know that automatic singing systems are also using music21 --I'd very much enjoy talking to you about what you're doing sometime!

[oxygen-dioxide]

For the "'-' to slurs", I found that music21 doesn't allow "-" as note lyric. I understand that we don't make it builtin because it isn't a standard, but if a developer wants to convert "-" to slurs in their own python code, they can't, because all the infos about "-" lyrics are cleared when loading the midi file into music21.

[mscuthbert]

Instead of setting ".lyric" on a note in MIDI output we should create a Lyric object and set the "rawText" to the value. That way it will preserve the hyphen.

Currently it should set the lyric to the Lyric continue type.