instructions for setting up local web-server

[StefanKarpinski]

This has been requested and we should have it:

http://julialang.org/blog/2012/02/why-we-created-julia/#comment-443074919

[ViralBShah]

We already have this:

https://github.com/JuliaLang/julia/blob/master/ui/README.web

Perhaps now that the README is no longer the homepage, we can put this in the main README. Also, I will work on adding a section to the documentation on how to use the graphics.