Method missing causes infinite recursion on sinatra 1.4.4, so introduce a "word" method to serve.

gems/sinatra-1.4.4/lib/sinatra/base.rb:1760: stack level too deep (SystemStackError)
We have to delete the word from the list when it's used to avoid repeats.

So we have to deep-dup the hash on each request.
Use shuffle instead of sort_by { rand }