Allow specifying version bump via BUMP for prepare_release target
erchef 1.1.2

Updated deps:

  amqp_client
    2013-01-07 7622ad8 Use public git URL for rabbit_common dep

  chef_wm
    2013-01-07 10780cd Merge branch 'dt/OC-4337/membership-check'
    2012-12-21 143e758 Changes for splitting off principal ejson by OSC/OPC
    2012-12-14 7968885 Changes for OSC compatibility
    2012-12-13 d9145d7 Added org membership check for users in principals endpoint