(test): use jest w/ coverage instead STILL NOT WORKING see #6

- jest's coverage reporting only knows how to use inline source maps,
  so make them output as inline instead of external .map files
  - can remove exorcist now since inline source maps are built-in
    to browserify

FIXME: jest --coverage on browserify.spec.js runs into an infinite loop
- likely bc it's relying on istanbul-lib-instrument and running it on
  ammo and failing spectacularly -- need it to ignore ammo code

FIXME: webpack passes like with nyc but ignores nothing... :/

.gitignore

@@ -1,5 +1,5 @@
 build/
-.nyc_output/
+coverage/
 
 ### Node ###
 

jest.config.js

@@ -0,0 +1,15 @@
+module.exports = {
+  // don't need to run babel on anything (and browserify bundle will error out if we do)
+  transform: {},
+  setupFilesAfterEnv: [
+    // polyfill worker
+    '@react-frontend-developer/jsdom-worker'
+  ],
+  coveragePathIgnorePatterns: [
+    '/node_modules/', // default
+    'webpack:/node_modules/',
+    'webpack:/webpack',
+    'webpack:/test-utils/',
+    '<rootDir>/test-utils/' // ignore test-utils
+  ]
+}