Exa port dependencies

[Joshua Root]

> The list below is the current list of build dependencies when I do a
> port install of "exa +doc+git". The list seems pretty ridiculous though.
> I just cloned the exa repository and did a cargo build outside macports.
> None of these dependencies are required.
The vast majority of those are dependencies of pandoc, which is used by 
the exa port's doc variant. They won't be installed when installing exa 
from a binary archive. If you need to build locally and don't want all 
these deps, you can use -doc.

- Josh