Update README to reference README.md

This older doc/README file is pure text and provides incomplete information compared to the root's README.md markdown file.  I copied over some introductory verbiage and added cross references to that file.
Update README.md; add google group link.

Mention that ./acprep is a Python script for installing dependencies.
Update README.md; more introduction and documentation link

Updated the introduction with the little information that was unique to doc/README.   Also added a link to the documentation page.
Remove doc/README

Remove obsolete and incorrect README file.  Correct information in
README.md, one directory up.
Small typos..
Merge pull request #262 from merriam/master

A pair of small documentation changes...