feat(datePipe): numeric string support

modules/@angular/facade/src/lang.dart

@@ -189,6 +189,13 @@ class NumberWrapper {
 
   static double get NaN => double.NAN;
 
+  static bool isNumeric(value) {
+    if(value == null) {
+      return false;
+    }
+    return double.parse(value, (e) => null) != null;
+  }
+
   static bool isNaN(num value) => value.isNaN;
 
   static bool isInteger(value) => value is int;

modules/@angular/facade/src/lang.ts

@@ -320,6 +320,8 @@ export class NumberWrapper {
 
   static get NaN(): number { return NaN; }
 
+  static isNumeric(value: any): boolean { return !isNaN(value - parseFloat(value)); }
+
   static isNaN(value: any): boolean { return isNaN(value); }
 
   static isInteger(value: any): boolean { return Number.isInteger(value); }

modules/@angular/facade/test/lang_spec.ts

@@ -1,6 +1,5 @@
 import {beforeEach, ddescribe, describe, expect, iit, it, xit} from '@angular/core/testing';
-
-import {RegExpMatcherWrapper, RegExpWrapper, StringWrapper, hasConstructor, isPresent, resolveEnumToken} from '../src/lang';
+import {NumberWrapper, RegExpMatcherWrapper, RegExpWrapper, StringWrapper, hasConstructor, isPresent, resolveEnumToken} from '../src/lang';
 
 enum UsefulEnum {
   MyToken,
@@ -51,6 +50,28 @@ export function main() {
     });
   });
 
+  describe('Number', () => {
+    describe('isNumeric', () => {
+      it('should return true when passing correct numeric string',
+         () => { expect(NumberWrapper.isNumeric('2')).toBe(true); });
+
+      it('should return true when passing correct double string',
+         () => { expect(NumberWrapper.isNumeric('1.123')).toBe(true); });
+
+      it('should return true when passing correct negative string',
+         () => { expect(NumberWrapper.isNumeric('-2')).toBe(true); });
+
+      it('should return true when passing correct scientific notation string',
+         () => { expect(NumberWrapper.isNumeric('1e5')).toBe(true); });
+
+      it('should return false when passing incorrect numeric',
+         () => { expect(NumberWrapper.isNumeric('a')).toBe(false); });
+
+      it('should return false when passing parseable but non numeric',
+         () => { expect(NumberWrapper.isNumeric('2a')).toBe(false); });
+    });
+  });
+
   describe('String', () => {
     var s: any /** TODO #9100 */;