Override default mimetype from settings
Override default mimetype from settings

- Add a new setting FREEZER_GUESSED_MIMETYPE
  that is used as the default mimetype instead
  of application/octet-stream.
- For example, this allows us to generate sites for servers
  where the default mimetype is text/html and we
  can't change the original view url to use the (.html)
  extension.

SimonSapin/Frozen-Flask,SimonSapin/Frozen-Flask,SimonSapin/Frozen-Flask