fix: Print explicit error if use with babel 6 is attempted (#207)

Author: coreyfarrell

.babelrc

@@ -0,0 +1,12 @@
+'use strict'
+
+module.exports = {
+  plugins: [
+    '@babel/plugin-transform-modules-commonjs'
+  ],
+  env: {
+    test: {
+      plugins: ['./lib']
+    }
+  }
+}