Updating README with build/run instructions

README.md

-# tangelo-site
-Tangelo website
+# The Tangelo Website
+
+This repository contains the source code for the Tangelo website, including
+infrastructure for showing Tangelo demos.  The site is technically a [Tangelo
+application](https://github.com/Kitware/tangelo) that serves an ``index.html``
+at its root.  This allows the demos to show off features of Tangelo directly.
+
+To build the site, first do ``npm install`` in the root of the repository,
+followed by ``grunt``.  If all goes well, the Tangelo site will wind up in
+``build/site``.
+
+To serve the site, use the ``serve`` script in the root of the repository as
+follows:
+
+    $ ./serve
+
+serves the site at ``localhost``, port 8080.
+
+    $ ./serve 10000
+
+serves it at ``localhost``, port 10000.  Finally,
+
+    $ ./serve 0.0.0.0 8000
+
+will serve it on ``localhost`` at port 8000, but the application will listen on
+all interfaces, exposing the site on any domain names ``localhost`` is known as
+on the local network.