chore(icon): export icon registry as part of icon (#366)

Author: kara

src/components/icon/icon.ts

@@ -11,7 +11,7 @@ import {
     AfterViewChecked
 } from '@angular/core';
 import {MdIconRegistry} from './icon-registry';
-
+export {MdIconRegistry} from './icon-registry';
 
 
 /** Exception thrown when an invalid icon name is passed to an md-icon component. */

src/demo-app/icon/icon-demo.ts

@@ -1,6 +1,5 @@
 import {Component, ViewEncapsulation} from '@angular/core';
-import {MdIcon} from '../../components/icon/icon';
-import {MdIconRegistry} from '../../components/icon/icon-registry';
+import {MdIcon, MdIconRegistry} from '../../components/icon/icon';
 
 @Component({
   selector: 'md-icon-demo',