Major Improvments

This is a pre-release so please report any issues!

#51 Timer fixes -- thanks! https://github.com/0xd34d10cc
#50 Optimized difs 2x improvment-- thanks! https://github.com/0xd34d10cc

• Decreased Memory usage when only capturing new frames
• Mac now uses AVCapture which decreases the cpu usage dramatically!
• Slimmed down the public API to make it as simple as possible
• Refactored internals of codebase to share more code across platforms
• Removed the Extract functions, save one! The extract functions are beyond the scope of this library so they are removed except one so that users can see how they can extract data and convert it to their format.
• Data is now explicit through the struct ImageBGRA