Add easing equations.

Modified libCinder's Easing.h to use std math functions from <cmath>
Include Easing in header. ch namespace alias.
Easing and ch:: propagation to samples.
Separate Phrase types into files.

All inside the phrase/ directory.
Prepping for infinite Phrases.
Test that things work as expected with infinite duration.

That is: Ramps never change value along an infinite timescale.
Loops continue cycling indefinitely.
Not that you should really be using an infinite duration.
Instead, add a finishFn to a Motion that sets its time back to 0.