Migrants refactor

Major refactor of Migrants code
- Bug Fix: multiple copies of fills and country texts when resizing
- Bug Fix: progress paths render off path
- code style clean-up
- more efficient, easier to read
- removed unused variables and functions
- rename migrants_refactor.js back to migrants.js

Make sure to test plenty before you merge it. I'm not 100% clear on how the orange wedges work, so that may not be quite right.

It couldn't hurt to read through the code. You'll need to merge on the command line and fix the conflicts manually. Contact me if you need help with that.