Make clear that contributing code to the Redis project means to release it...

Make clear that contributing code to the Redis project means to release it under the terms of the BSD license.

CONTRIBUTING

+Note: by contributing code to the Redis project in any form, including sending
+a pull request via Github, a code fragment or patch via private email or
+public discussion groups, you agree to release your code under the terms
+of the BSD license that you can find in the COPYING file included in the Redis
+source distribution.
+
 # IMPORTANT: HOW TO USE REDIS GITHUB ISSUES
 
 * Github issues SHOULD ONLY BE USED to report bugs, and for DETAILED feature

README

@@ -128,4 +128,16 @@ system reboots.
 You'll be able to stop and start Redis using the script named
 /etc/init.d/redis_<portnumber>, for instance /etc/init.d/redis_6379.
 
+Code contributions
+---
+
+Note: by contributing code to the Redis project in any form, including sending
+a pull request via Github, a code fragment or patch via private email or
+public discussion groups, you agree to release your code under the terms
+of the BSD license that you can find in the COPYING file included in the Redis
+source distribution.
+
+Please see the CONTRIBUTING file in this source distribution for more
+information.
+
 Enjoy!