TextEncoder polyfill

Apparently Safari doesn't sport a TextEncoder, so here's a polyfill for it.

test/utils/TextEncoderPolyfill-test.js

@@ -0,0 +1,39 @@
+/*
+Copyright 2017 Vector Creations Ltd
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+"use strict";
+
+import TextEncoderPolyfill from 'utils/TextEncoderPolyfill';
+
+import * as testUtils from '../test-utils';
+import expect from 'expect';
+
+describe('textEncoderPolyfill', function() {
+    beforeEach(function() {
+        testUtils.beforeEach(this);
+    });
+
+    it('should correctly encode a range of strings', function() {
+        const encoder = new TextEncoderPolyfill();
+
+        expect(encoder.encode('ABC')).toEqual(Uint8Array.of(65, 66, 67));
+        expect(encoder.encode('æ')).toEqual(Uint8Array.of(0xC3, 0xA6));
+        expect(encoder.encode('€')).toEqual(Uint8Array.of(0xE2, 0x82, 0xAC));
+
+        // PILE OF POO (💩)
+        expect(encoder.encode('\uD83D\uDCA9')).toEqual(Uint8Array.of(0xF0, 0x9F, 0x92, 0xA9));
+    });
+});