Support for multi-byte buffers. #17

- updates "data" handler to loop over data array, instead of copying data[0]
- push each byte into into currentBuffer
- inspect currentBuffer in each loop iteration for [START_SYSEX, …, END_SYSEX] or MIDI commands
- when [START_SYSEX, …, END_SYSEX] or MIDI are found, invoke command and clear currentBuffer

Signed-off-by: Rick Waldron <waldron.rick@gmail.com>
Support for multi-byte buffers - tests

Signed-off-by: Rick Waldron <waldron.rick@gmail.com>
Merge pull request #18 from rwldrn/17

LGTM...pretty much exactly what I was planning on doing.  Thanks Rick!  There is actually a bug about the bufferSize that was introduced in streams2 https://github.com/joyent/node/issues/5098 but this is a good change anyways.  I will push this to npm later.