Added frequency, pitch, waveform, signal and math modules. About a third through Oscillator mod
Added Frequency struct, HasFrequency trait and frequency related calculator functions.
Updated with new modules
fixed docs
Added Oscillator struct, not yet complete
Add Pitch struct, HasPitch trait and associated calculator functions.
Added Signal struct, a helper struct for generating basic signals
Started the Waveform module
Merge pull request #11 from mitchmindtree/master

Frequency, Pitch, Signal, Waveform(WIP), Oscillator(WIP)