added script to convert README.rst files to README.html.  Needs more work...
Need to run 'make .htmls' first to create html files, links to clawpack style, css files, etc. are currently broken in clawcode2html.py
convert_rst2html.py: check for missing .rst file and don't include _output or multiple _plots directories in list
Merge pull request #66 from rjleveque/convert_rst2html

Script to convert README.rst to README.html in application directory