explicitly use 0.10 branch in docs

Author: karussell

docs/core/quickstart-from-source.md

@@ -11,7 +11,7 @@ Now, before you proceed install git and jdk8, then do:
 
 ```bash
 $ git clone git://github.com/graphhopper/graphhopper.git
-$ cd graphhopper; git checkout master
+$ cd graphhopper; git checkout 0.10
 $ ./graphhopper.sh web europe_germany_berlin.pbf
 now go to http://localhost:8989/
 ```