add .npy binary for Tau Ceti data
separate classes into files; rename Simulation to Raytracer
done spherical coordinate system
fix plethora of sign errors
dependency cleanup
make spot interface more reasonable
rename local variable mask to attens
Revert "rename local variable mask to attens"

This reverts commit 123cf6e0bf46833ce9148d6f329ebdaf0eb95325.
use itertools.izip instead of zip
improve spec.py demo
rename mask-finding function to trace
faster RV algorithm wip
add grid render demo
add readme
fix readme code block formatting
fix render, improve grid demo
Merge branch 'master' of https://github.com/aidabehmard/starspot
add cut Tau Ceti data
change starspot size convention to fractional area
Merge branch 'master' of https://github.com/aidabehmard/starspot