Update README for 1.7.1

Author: dumerrill

README.md

@@ -1,7 +1,7 @@
 <hr>
 <h3>About CUB</h3>
 
-Current release: v1.6.4 (12/06/2016)
+Current release: v1.7.1 (08/18/2017)
 
 We recommend the [CUB Project Website](http://nvlabs.github.com/cub) and the [cub-users discussion forum](http://groups.google.com/group/cub-users) for further information and examples.