Implement Sound class

[ddemidov]

See #15

[rhempel]

Thanks - this is helpful - we may want to consider adding parameters to the speak function to control volume, speed, inter-word space, and possibly language?

I really appreciate the work you are doing on this binding !

[ddemidov]

The espeak parameters I just dragged from C++ implementation. We can indeed provide second optional parameter for espeak arguments.