Add README.md file for signposts elsewhere

Throw in a README.md file to tell people a little about the code,
where the master repository is, how to install the code (or at
least where to look to get that info), where to get help, and what
license is used for the code.

README.md

@@ -0,0 +1,29 @@
+# Distributed Proofreaders
+
+Preserving history, one page at a time.
+
+This repository contains the code that powers http://www.pgdp.net and other
+sister DP sites world-wide.
+
+The master repository is hosted on SourceForge at: 
+https://sourceforge.net/p/dproofreaders/git/
+
+## Installation
+
+See `SETUP/installation.txt` for information on system pre-requisites and
+installation instructions. This file also has information on upgrading from
+an earlier release of the code.
+
+If you need assistance with the code, inquire within the
+[DP Site Code](http://www.pgdp.net/phpBB3/viewforum.php?f=32) forum at pgdp.net.
+
+## Code development
+
+To get involved with development on this code base, see
+[DP Code Development](http://www.pgdp.net/wiki/DP_Code_Development) in the
+pgdp.net wiki.
+
+## License
+
+All source code published here is available under the terms of the GNU General
+Public License, version 2. See `license.txt` for more information.