Second release

Summary of changes since first release (not an exhaustive list):

• dropped Pyo in favor of Pyglet audio
• expanded EyeLink support
• new stimulus creation, analysis and visualization methods, including convolve_hrtf, fit_sigmoid, and barplot
• some changes to the API of ExperimentController (most notably the replacement of flip_and_play with start_stimulus)

First release

Experiments using this release:

• DivAttnSemantic (drmccloy)