fixes the leveldb link

previously https://code.google.com/p/leveldb/ was linked, but the project was moved to https://github.com/google/leveldb

Author: seriousManual

README.md

@@ -28,7 +28,7 @@ LevelUP
 Introduction
 ------------
 
-**[LevelDB](http://code.google.com/p/leveldb/)** is a simple key/value data store built by Google, inspired by BigTable. It's used in Google Chrome and many other products. LevelDB supports arbitrary byte arrays as both keys and values, singular *get*, *put* and *delete* operations, *batched put and delete*, bi-directional iterators and simple compression using the very fast [Snappy](http://code.google.com/p/snappy/) algorithm.
+**[LevelDB](https://github.com/google/leveldb)** is a simple key/value data store built by Google, inspired by BigTable. It's used in Google Chrome and many other products. LevelDB supports arbitrary byte arrays as both keys and values, singular *get*, *put* and *delete* operations, *batched put and delete*, bi-directional iterators and simple compression using the very fast [Snappy](http://code.google.com/p/snappy/) algorithm.
 
 **LevelUP** aims to expose the features of LevelDB in a **Node.js-friendly way**. All standard `Buffer` encoding types are supported, as is a special JSON encoding. LevelDB's iterators are exposed as a Node.js-style **readable stream** a matching **writeable stream** converts writes to *batch* operations.