fix(Pipes): mark date & slice as non-pure

Author: vicb

modules/angular2/src/core/pipes/date_pipe.ts

@@ -78,7 +78,7 @@ var defaultLocale: string = 'en-US';
  *     {{ dateObj | date:'mmss' }}        // output is '43:11'
  */
 @CONST()
-@Pipe({name: 'date'})
+@Pipe({name: 'date', pure: false})
 @Injectable()
 export class DatePipe implements PipeTransform {
   /** @internal */

modules/angular2/src/core/pipes/slice_pipe.ts

@@ -67,7 +67,7 @@ import {Pipe} from '../metadata';
  *     {{ 'abcdefghij' | slice: 100 }}    // output is ''
  */
 
-@Pipe({name: 'slice'})
+@Pipe({name: 'slice', pure: false})
 @Injectable()
 export class SlicePipe implements PipeTransform {
   transform(value: any, args: any[] = null): any {