Use Terminal type in attach, fit and fullscreen

src/addons/attach/attach.test.ts

@@ -12,7 +12,7 @@ class MockTerminal {}
 describe('attach addon', () => {
   describe('apply', () => {
     it('should do register the `attach` and `detach` methods', () => {
-      attach.apply(MockTerminal);
+      attach.apply(<any>MockTerminal);
       assert.equal(typeof (<any>MockTerminal).prototype.attach, 'function');
       assert.equal(typeof (<any>MockTerminal).prototype.detach, 'function');
     });