Moved babel config back out into .babelrc

This is due to .babelrc being used for other tooling.

.babelrc

@@ -0,0 +1,19 @@
+{
+  "presets": [
+    "@babel/preset-env",
+    "@babel/preset-react"
+  ],
+  "plugins": [
+    "react-hot-loader/babel",
+    "@babel/plugin-proposal-class-properties"
+  ],
+  "env": {
+    "test": {
+      "plugins": [
+        ["istanbul", {
+          "exclude": ["node_modules/**", "test/**"]
+        }]
+      ]
+    }
+  }
+}