Switch from jasmine to jest (#747)

Summary:
The reasons for switching to jest:
- easy snapshot testing so that we can easily verify the structure of the parse tree and MathML tree
- easy compilation of ES6 features for tests as we continue to expand our use of ES6

Test Plan:
- npm test

package.json

@@ -16,6 +16,7 @@
   "license": "MIT",
   "devDependencies": {
     "babel-eslint": "^7.2.0",
+    "babel-jest": "^20.0.3",
     "babel-plugin-transform-class-properties": "^6.23.0",
     "babel-plugin-transform-runtime": "^6.15.0",
     "babel-preset-es2015": "^6.18.0",
@@ -26,8 +27,7 @@
     "eslint": "^3.13.0",
     "express": "^4.14.0",
     "glob": "^7.1.1",
-    "jasmine": "^2.3.2",
-    "jasmine-core": "^2.3.4",
+    "jest": "^20.0.4",
     "js-yaml": "^3.3.1",
     "jspngopt": "^0.2.0",
     "less": "~2.7.1",
@@ -46,5 +46,13 @@
   },
   "dependencies": {
     "match-at": "^0.1.0"
+  },
+  "jest": {
+    "testMatch": [
+      "**/test/*-spec.js"
+    ],
+    "transform": {
+      "^.+\\.js$": "babel-jest"
+    }
   }
 }