Based on my rewrite of the Agnoster theme, uses simpler segment drawing
functions and only relies on local variables. Uses git-info module in
non-verbose mode, so a repo with only untracked files will not count as
dirty (but dirty state is computed faster). Also took the freedom of
adding an extra space character after the 'r' for the Ranger segment,
and after the dirty indicator for the Git segment. Everything else looks
and behaves exactly the same as the original prompt.
