x/lint: update vim rtp path in README.md to use x/lint

Change-Id: I8156a1a6328fd03c153ddb648de2db43a3968536
GitHub-Last-Rev: e8f26b7
GitHub-Pull-Request: #405
Reviewed-on: https://go-review.googlesource.com/121818
Reviewed-by: Andrew Bonventre <andybons@golang.org>

Author: michal-franc

README.md

@@ -61,7 +61,7 @@ before we can accept your contribution.
 
 Add this to your ~/.vimrc:
 
-    set rtp+=$GOPATH/src/github.com/golang/lint/misc/vim
+    set rtp+=$GOPATH/src/golang.org/x/lint/misc/vim
 
 If you have multiple entries in your GOPATH, replace `$GOPATH` with the right value.