add settings for vagrant

- add separate coffeestats.settings.vagrant that uses the file based
  email backend
load missing staticfiles template tags in password_reset_form.html
don't enforce timezone middleware for static files
drop ReCaptcha usage

- remove django-recaptcha dependency
- remove ReCaptcha fields from registration form
- modify tests and view code
- remove recaptcha environment variables and pillars data
- remove recaptcha classes from sass input and generated CSS