Improved formatting and appearance of jpylyzer demo

Mainly updated and shortened some text, deleted some other text and improved general formatting. Also re-worked the HTML into valid HTML and put it through HTMLTidy. Finally added warning on possible crashes/freezes when using the demo under linux (as per [this issue](https://github.com/openplanets/scape-demo-sites/issues/6)).

Note: while preparing this pull request I'm noticing that the diff stats indicate changes for files the StyleJS directory. Apparently these changes are all caused by CRLF / LF linebreak replacements (haven't seen this before, but looks harmless to me).