Convert CommonJS exports to ES6-compatible exports

We use `export default` begrudgingly here. Ideally we'd use just `export`, though this entire SDK expects things to be exported as a default. Instead of breaking everything, we'll sacrifice our export pattern for a smaller diff - a later commit can always do the default export -> regular export conversion.

src/components/views/voip/CallPreview.js

@@ -1,5 +1,6 @@
 /*
 Copyright 2017, 2018 New Vector Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -22,7 +23,7 @@ import CallHandler from '../../../CallHandler';
 import dis from '../../../dispatcher';
 import sdk from '../../../index';
 
-module.exports = createReactClass({
+export default createReactClass({
     displayName: 'CallPreview',
 
     propTypes: {

src/components/views/voip/CallView.js

@@ -1,5 +1,6 @@
 /*
 Copyright 2015, 2016 OpenMarket Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -22,7 +23,7 @@ import sdk from '../../../index';
 import MatrixClientPeg from '../../../MatrixClientPeg';
 import { _t } from '../../../languageHandler';
 
-module.exports = createReactClass({
+export default createReactClass({
     displayName: 'CallView',
 
     propTypes: {

src/components/views/voip/IncomingCallBox.js

@@ -1,6 +1,7 @@
 /*
 Copyright 2015, 2016 OpenMarket Ltd
 Copyright 2018 New Vector Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -22,7 +23,7 @@ import dis from '../../../dispatcher';
 import { _t } from '../../../languageHandler';
 import sdk from '../../../index';
 
-module.exports = createReactClass({
+export default createReactClass({
     displayName: 'IncomingCallBox',
 
     propTypes: {

src/components/views/voip/VideoFeed.js

@@ -1,5 +1,6 @@
 /*
 Copyright 2015, 2016 OpenMarket Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -18,7 +19,7 @@ import React, {createRef} from 'react';
 import PropTypes from 'prop-types';
 import createReactClass from 'create-react-class';
 
-module.exports = createReactClass({
+export default createReactClass({
     displayName: 'VideoFeed',
 
     propTypes: {

src/components/views/voip/VideoView.js

@@ -1,5 +1,6 @@
 /*
 Copyright 2015, 2016 OpenMarket Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -34,7 +35,7 @@ function getFullScreenElement() {
     );
 }
 
-module.exports = createReactClass({
+export default createReactClass({
     displayName: 'VideoView',
 
     propTypes: {