Updates a comment.
Refactors sourcing the zsh theme.
Going zsh!
Updated custom dir example hierarchy.
Updates README in Customization section
Adds example customization file.
Removes code duplication.
Adds a symbolic link for backward compatibility.
Adds the actual plugin dirs to the fpath.

Actually can someone clarify this? I don't see a difference, whether I
add the plugin path to fpath, the plugin file or nothing at all.
Everything working fine, no matter what I do.
Gets rid of some unneeded string declarations.