Fixes for CentOS

* Fix WS_HOME when /etc/sudoers has "always_sets_home" or "env_reset" configured
* changed '== "ubuntu"' to '!= "mac_os_x"' to generalize for other versions of Linux
* added missing template "history_settings.bash"
* use latest version of Ruby (p374) for rvm attributes

I hope that you'll find these changes useful; I'm able to use them to configure my computer on CentOS 6.

Pat