Use ES6 import/export (#139)

* Use ES6 import/export

* Fix tests

packages/util/src/buffer/fromU8a.js

@@ -3,7 +3,7 @@
 // of the ISC license. See the LICENSE file for details.
 // @flow
 
-const bufferFromU8a = require('../u8a/toBuffer');
+import bufferFromU8a from '../u8a/toBuffer';
 
 /**
   @name bufferFromU8a
@@ -11,4 +11,4 @@ const bufferFromU8a = require('../u8a/toBuffer');
   @summary Creates a Buffer object from a Uint8Array.
   @alias u8a/toBuffer
 */
-module.exports = bufferFromU8a;
+export default bufferFromU8a;

packages/util/src/buffer/fromU8a.spec.js

@@ -2,9 +2,9 @@
 // This software may be modified and distributed under the terms
 // of the ISC license. See the LICENSE file for details.
 
-const isFunction = require('../is/function');
+import isFunction from '../is/function';
 
-const { bufferFromU8a } = require('./index');
+import { bufferFromU8a } from './index';
 
 describe('bufferFromU8a', () => {
   it('exists as a function', () => {

packages/util/src/buffer/index.js

@@ -3,13 +3,13 @@
 // of the ISC license. See the LICENSE file for details.
 // @flow
 
-const bufferFromU8a = require('./fromU8a');
-const bufferToU8a = require('./toU8a');
+import bufferFromU8a from './fromU8a';
+import bufferToU8a from './toU8a';
 
 /**
   @summary Utility methods to convert to and from `Buffer` objects
 */
-module.exports = {
+export {
   bufferFromU8a,
   bufferToU8a
 };

packages/util/src/buffer/toU8a.js

@@ -14,10 +14,10 @@
 
     bufferToU8a(Buffer.from([1, 2, 3]));
 */
-module.exports = function bufferToU8a (buffer?: Buffer): Uint8Array {
+export default function bufferToU8a (buffer?: Buffer): Uint8Array {
   if (!buffer) {
     return new Uint8Array([]);
   }
 
   return new Uint8Array(buffer);
-};
+}

packages/util/src/buffer/toU8a.spec.js

@@ -2,7 +2,7 @@
 // This software may be modified and distributed under the terms
 // of the ISC license. See the LICENSE file for details.
 
-const { bufferToU8a } = require('./index');
+import { bufferToU8a } from './index';
 
 describe('bufferToU8a', () => {
   it('returns an empty buffer when null provided', () => {