This commit refactors the theme & status line configuration
into their own lua files so they can be more readily
customized by the user. As kickstart has grown, it's becoming
harder and harder to keep up with changes to the main init.lua
file if you're maintaining local customizations. We should still
encourage users to modify init.lua to suit their needs, but also
make it possible to leave it unmodified if that's their choice.
Chris Patti