Remove transform-runtime

We use instance methods (or at least, draft.js does) so we need
babel-polyfill instead.

src/vector/index.js

@@ -16,6 +16,15 @@ limitations under the License.
 
 'use strict';
 
+// for ES6 stuff like startsWith() that Safari doesn't handle
+// and babel doesn't do by default
+// Note we use this, not the babel transform-runtime plugin
+// since transform-runtime does not cover instance methods
+// such as "foobar".includes("foo") which bits of our library
+// code use.
+// https://babeljs.io/docs/plugins/transform-runtime/
+require('babel-polyfill');
+
 // CSS requires: just putting them here for now as CSS is going to be
 // refactored soon anyway
 require('../../vector/components.css');