Notes, BPM, ms_per_tick

[Datseris]

I have added an alias Notes = Vector{Note}. It feels very natural for me plus I was using it all the time for research. I think it is nice, plus it is only something optional.

I have also added two functions: BPM(midi) and ms_per_tick(midi) which were super important for me, and I think fit perfectly on this package.

Soon I will upload a new package about manipulating music (using MIDI). I had these 2 there but I feel they fit much more here.

Please let me know if you agree, and if yes go ahead and merge!

[Datseris]

@JoelHobson okay that is everything. I improved significantly the README as well, I think.

[JoelHobson]

Could you add a comment explaining the reasoning behind tttttt? I see your comment below referring to it as tt-tt-tt, but I still don't quite follow what it means.

[JoelHobson]

Those sound like excellent utility functions to include. I'm happy to merge your changes, I just have one nitpicking comment.

I'm also really happy that you're still using this library and contributing to it!

[Datseris]

@JoelHobson I added an explanation.
HOwever I cannot explain the lines:

  # Get the microsecond number from tttttt
  unshift!(tttttt , 0x00)
  u = ntoh(reinterpret(UInt32, tttttt)[1])

because I do not know what they do, you do. You told me to use them over one and a half years ago when I started using this library!

[JoelHobson]

@Datseris Hahaha, no worries, I just meant an explanation of what 'tttttt' represented. Your explanation is fine. I'll merge this in. Thanks again!