added contributor section in README and package.json

@four43, @zhuzhe1983, @arjunmehta

Author: Sun Ning

README.md

@@ -63,5 +63,9 @@ Decode uint64-like hash into a bounding box that matches it. Data is returned as
 ## About Geohash
 
 Check [Wikipedia](http://en.wikipedia.org/wiki/Geohash "Wiki page for geohash") for more information.
-    
 
+## Contributors
+
+* [Seth Miller](https://github.com/four43)
+* [Zhu Zhe](https://github.com/zhuzhe1983)
+* [Arjun Mehta](https://github.com/arjunmehta)

package.json

@@ -1,6 +1,8 @@
 {
   "author": "Sun Ning <[email protected]> (http://sunng.info/)",
-  "contributors": ["Arjun Mehta <[email protected]> (http://www.arjunmehta.net/)"],
+  "contributors": ["Arjun Mehta <[email protected]> (http://www.arjunmehta.net/)",
+                   "Seth Miller",
+                   "Zhu Zhe <[email protected]>"],
   "name": "ngeohash",
   "description": "geohash library for nodejs",
   "keywords": [