Updated EZAudioFile for thread-safety and added more properties

• Added mutex lock for seek/read operations
• Added multi-channel support for getting waveform data
• Removed dependency on AEFloatConverter (replaced with EZAudioFloatConverter)
• Updated examples

Rewrote EZAudioPlot

• Completely rewrote EZAudioPlot using Core Animation layers for much better performance and customization.
• Made EZAudioPlot easier to subclass.
• Added EZAudioDisplayLink to optimize real-time plots
• Added EZPlotHistoryInfo to better manage rolling plots using internal circular buffer implementation.