Created vector graphics of logo

Created some basic vector drawings of the logo, both by itself and with
the name.
Added vector graphics to document

Added the nice shiny vector images to the requirements document. There is
the box by itself, and the entire text logo.
Added .gitignore to images directory

We don't need to store the .eps files in the images directory, so there's
a .gitignore in there now to keep them out of the repo.