Swing in MIDI import

Here are some examples of swing detection results.

Triplet swing (2:1)
before: https://docs.google.com/file/d/0B5alKuFoSol2S3M1X0xucEFFNHc/edit?usp=sharing
after: https://docs.google.com/file/d/0B5alKuFoSol2c0QtVThEaXpHVDg/edit?usp=sharing

Shuffle (3:1)
before: https://docs.google.com/file/d/0B5alKuFoSol2Sm9Hcmpla0lrbFU/edit?usp=sharing
after: https://docs.google.com/file/d/0B5alKuFoSol2S2hmcGlzeXl2TW8/edit?usp=sharing

Larger piece
before: https://docs.google.com/file/d/0B5alKuFoSol2VzFMa0xPcEdQYm8/edit?usp=sharing
after: https://docs.google.com/file/d/0B5alKuFoSol2UV91MFlLZ1FFS2s/edit?usp=sharing