Fix email address in package.json

Author: dphilipson

package.json

@@ -16,7 +16,7 @@
     "string",
     "enum"
   ],
-  "author": "David Philipson <dphilipson@gmail.com> (http://dphil.me)",
+  "author": "David Philipson <david.philipson@gmail.com> (http://dphil.me)",
   "license": "MIT",
   "bugs": {
     "url": "https://github.com/dphilipson/typescript-string-enums/issues"