Fedora 18 support

No real changes needed other than updating if statements-- what worked
with F17 works with F18.

Added the net-tools package dependency which provides netstat.

Added the tar package dependency when using rbenv (specifically needed
by the ruby-build plugin).
Merge pull request #47 from cwolferh/f18_support

Fedora 18 support
bash style cleanup
more code cleanups