chore(harp): use official pre-release 0.21 of harp (#2376)

Author: chalin

package.json

@@ -48,7 +48,7 @@
     "gulp-tslint": "^5.0.0",
     "gulp-util": "^3.0.6",
     "gulp-watch": "^4.3.4",
-    "harp": "git://github.com/filipesilva/harp.git#8da8d3497ddbfcbcbadd8be63e0fd731d7310cc4",
+    "harp": "0.21.0-pre.1",
     "html2jade": "^0.8.4",
     "indent-string": "^2.1.0",
     "jasmine-core": "^2.3.4",
@@ -77,4 +77,4 @@
     "jstransformer-marked": "^1.0.1"
   },
   "homepage": "http://angular.io/"
-}
+}