sinatra-url-for constructs absolute paths and full URLs for
handlers in a Sinatra application. Assuming that your application
is running on example.com, and that it has been mapped to /myapp,
you should be able call url_for from within a handler as follows:
url_for "/" # Returns "/myapp/"
url_for "/foo" # Returns "/myapp/foo"
url_for "/foo", :full # Returns "http://example.com/myapp/foo"
Submitted by: Eric Freeman <freebsdports at chillibear.com>