fix: circular dependency

Author: crisbeto

src/lib/progress-spinner/index.ts

@@ -35,5 +35,10 @@ export class MdProgressSpinnerModule {
 }
 
 
-export * from './progress-circle';
 export * from './progress-spinner';
+
+/** @deprecated */
+export {
+  MdProgressSpinnerModule as MdProgressCircleModule,
+  MdProgressSpinner as MdProgressCircle,
+};