Basic sinatra app

Basic app on sinatra.

Routes

/hello

Basicaly outputs "Hello world!"

/hello/:name

ex: /hello/Alex => 'Hello Alex'

/calculate

Can take params like 'from', 'to', 'action'

ex: /calculate?from=10&to=5&action=pl => 15

/qr

Can take params like 'word'

ex: /qr/hello => respond with qr code of word hello