fix: loosen angular peer dependency to support angular 4

Author: Matt Lewis

package.json

@@ -125,9 +125,9 @@
     "zone.js": "^0.7.2"
   },
   "peerDependencies": {
-    "@angular/common": "^2.0.0",
-    "@angular/core": "^2.0.0",
-    "@angular/platform-browser": "^2.0.0"
+    "@angular/common": ">=2.0.0 <5.0.0",
+    "@angular/core": ">=2.0.0 <5.0.0",
+    "@angular/platform-browser": ">=2.0.0 <5.0.0"
   },
   "files": [
     "dist",