Bind ReplicationConfig explicitly

Binding ReplicationConfig explicitly does not change Guice's default
behavior. We may still want to use this if we prefer our ReplicationModule
class to serve as an explicit manifest for the services it provides. Also,
in rare cases, Guice may be unable to validate a binding at injector
creation time unless it is given explicitly.

Please refer http://google-guice.googlecode.com/git/javadoc/com/google/inject/Binder.html

Change-Id: If3548b8b120fca634b833c358f7c8c89485049c8