Add a few helper methods to determine what directory we should use for iconsdir.
Update README.md with instructions on building docs in Ubuntu.
Update README.md

Messed up the asciidoc.conf bit. Oops...
Add instructions for building docs in Fedora.
Differentiate between homebrew and macports users and find their directory.
Merge pull request #113 from kelcecil/linux-doc

Support for building documentation on Linux systems