added (the beginnnings of) a shell script
more docs; made the page.open() call clearer
big changes to bash script, and cssdiff in general

* bash debugging via DEBUG env variable
* script is now callable from anywhere via symlink
* cleaned up/abstracted things a bit
* now using phantomjs's "--web-security=no" option which allows us the
  two pages we're diffing to be on different servers.
name change: cssdiff --> regrecss; doc update
move tool description out of <head>

too much clutter. no need for SEO crap; this is a local tool.
made CSS and URL regexps case-insensitive