Add typings test setup

src/Terminal.integration.ts

@@ -4,11 +4,13 @@
  * This file contains integration tests for xterm.js.
  */
 
+import * as cp from 'child_process';
 import * as glob from 'glob';
 import * as fs from 'fs';
 import * as os from 'os';
 import * as path from 'path';
 import * as pty from 'node-pty';
+import { assert } from 'chai';
 import { Terminal } from './Terminal';
 import { CHAR_DATA_CHAR_INDEX } from './Buffer';
 
@@ -143,3 +145,12 @@ if (os.platform() !== 'win32') {
     }
   });
 }
+
+describe('typings', () => {
+  it('should throw no compile errors', () => {
+    let result = cp.spawnSync(path.join(__dirname, '..', 'node_modules', '.bin', 'tsc'), {
+      cwd: path.join(__dirname, '..', 'fixtures', 'typings-test')
+    });
+    assert.equal(result.status, 0, `build did not succeed:\nstdout: ${result.stdout.toString()}\nstderr: ${result.stderr.toString()}\n`);
+  });
+});