DON'T use forced push for GitHub replication.

Typically people using GitHub keep on pushing to it
directly, even when configured as Gerrit slave.
Unfortunately the Gerrit default setting is "force push"
(+refs/*:refs/*) which causes unpleasant surprises.

Use normal push (refs/*:refs/*) for replication and leave 
the responsibility to the user to rebase the Gerrit 
repository when needed.

Change-Id: Ib7c4ed69c777d2bf5ffd98921821971d5f9c658e

github-plugin/src/main/java/com/googlesrouce/gerrit/plugins/github/git/ReplicationConfig.java

diff --git a/github-plugin/src/main/java/com/googlesrouce/gerrit/plugins/github/git/ReplicationConfig.java b/github-plugin/src/main/java/com/googlesrouce/gerrit/plugins/github/git/ReplicationConfig.java
index 2f3dcaa..79c9324 100644
--- a/github-plugin/src/main/java/com/googlesrouce/gerrit/plugins/github/git/ReplicationConfig.java
+++ b/github-plugin/src/main/java/com/googlesrouce/gerrit/plugins/github/git/ReplicationConfig.java
@@ -59,6 +59,7 @@
             "remote", organisation, "projects")));
     projects.add(projectName);
     replicationConf.setStringList("remote", organisation, "projects", projects);
+    replicationConf.setString("remote", organisation, "push", "refs/*:refs/*");
     replicationConf.save();
   }