Adding documentation for Contributors.
Adding xsl stylesheets to render xdoc in browser and css to style content, this makes testing documentation additions easier without rendering the entire site. Simply open up xdoc in browser to see what it will look like after rendering.
git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/math/trunk@141018 13f79535-47bb-0310-9956-ffa450edef68
Joerg Pietschmann
Dirk Verbeeck
Mark R. Diggory