Fix the "go get" path in the README.

README

@@ -1,7 +1,7 @@
 The LevelDB key-value database in the Go programming language.
 
 To download and install from source:
-$ go get https://github.com/golang/leveldb
+$ go get github.com/golang/leveldb
 
 Unless otherwise noted, the LevelDB-Go source files are distributed
 under the BSD-style license found in the LICENSE file.