Big undertaking to support Mercury in the browser. Builds are working and all tests are passing both for web and node builds. Most code is closely shared.
This commit also swaps in yarn for npm and tweaks circle ci a bit.
* appveyor.yml first go
* changing node
* ps
* narrow it down
* trying this
* fix airbnb module
* trying with yarn
* logging
* hybrid?
* trying yarn w/circle
* bump workers?
* build off?
* updating script
* tweaking script for appveyor
* bumping maxworkers
* cleaning up
* build step?
* yarn it
* added appveyor badge
