Merge pull request #536 from andrejserafim/doc

Documenting local build

CONTRIBUTING.md

@@ -0,0 +1,13 @@
+## Build Prerequisites ##
+Have at least a local copy of built redis, for more information see [tutorial](https://www.digitalocean.com/community/tutorials/how-to-install-and-use-redis).
+
+Note that redis shouldn't be running - the build will start instances as needed.
+
+## Running the tests ##
+
+``` bash
+export REDIS_BIN=<path to redis binaries>
+
+# And finally running the build
+mvn -DargLine="-Xmx2g -DredisBinary=$REDIS_BIN/redis-server" -Punit-test clean test -e -X
+```