add interpretation and execution

If a note object has a 'language' field, then the content of the note will be passed to that language's interpreter, and the results output in place of the text of the note.
remove jquery.html test file

this was accidentally committed
remove test yasi demo

yasi (uncertain provenance) was a demo app of how to use Sinatra; removing from source control
add Gemfile
make web_note readonly, to be updated through ssh alone