fix: add explicit peer dependency on typescript 2.3.x

Closes #221

Author: Matt Lewis

package.json

@@ -128,7 +128,8 @@
     "@angular/animations": "^4.0.0",
     "@angular/common": "^4.0.0",
     "@angular/core": "^4.0.0",
-    "@angular/platform-browser": "^4.0.0"
+    "@angular/platform-browser": "^4.0.0",
+    "typescript": "^2.3.0"
   },
   "files": [
     "dist",