publish-site: set default MIME type for uploaded files

This avoids libcloud crashing when upload_object is called with
something it can't guess by defaulting to `application/octet-stream`
update-template: add --verbose, --all-posts options
Rename update-template to apply-template, add creation / timestamps

* Better script name
* Add support for creating new files
* Add support for updating timestamps
setup.py modernization
Switch to Cliff, overhaul command structure

* Migrate all utilities under the "simple-cloud-site" top-level command
* Migrate most progress information to logging
* Consistent version numbering based on setup.py
* frosted / isort cleanup