Update gopkg.in link in README now that v1 is tagged.

Thanks to @borgstrom for noticing this.

Change-Id: I6c18f1133e7b66f365cda2c46d835de0ccb17d65
Reviewed-on: http://review.couchbase.org/55674
Reviewed-by: Mark Nunberg <mark.nunberg@couchbase.com>
Tested-by: Brett Lawson <brett19@gmail.com>

README.md

@@ -21,7 +21,7 @@ Bug Tracker - [http://www.couchbase.com/issues/browse/GOCBC](http://www.couchbas
 
 To install the latest development version, run:
 ```bash
-go get gopkg.in/couchbaselabs/gocb.v0
+go get gopkg.in/couchbaselabs/gocb.v1
 ```