Increase JSON nesting to allow for heavily nested patterns

Nesting limit changed from default of 20 to 1000, which is more than
enough to work with the examples in #3 #4 (except the giant email
regex which fails because it's invalid JS regex syntax)

Also display helpful error to insane users who manage to breach the
limit (although the parser hits the Ruby recursion limit eventually)
Monospace font for input box

Closes #9
Merge pull request #20 from dbr/nestedness

Increase JSON nesting to allow for heavily nested patterns
Forcing encoding of the raw regexp string to UTF-8

Closes #16
Adding support for wrapping expressions in literal syntax

Closes #5
Allowing unescaped "{" and "}" characters

Closes #13
Adding some more content to the README

People are starting to ask about contributing!
General layout and usability improvements
Loading initial JS requirements in one call to server
Adding a loading indicator.

The JS in main.js is getting a little hairy, it will need to be cleaned
up once these initial features are all implemented. For now though, I
can live it with.

Closes #11