Convert lib/conf.rb to use XDG specification.

Conform to XDG specification standards for application
files.  By default it will put files in the
$XDG_DATA_HOME/clearskies directory.

In the event $XDG_DATA_HOME is not set it is defaulted to
$HOME/.local/share per the specification.
Merge pull request #37 from ketiko/xdg_specification

Convert lib/conf.rb to use XDG specification.