Django-s3file

* Fix missing minified JavaScript in pypi packages

* Fix deployment check return value

* Make AWS_LOCATION setting optional

New features

* Add upload progress JavaScript events to build progress bars
* Add S3 backend mock for local development and JavaScript ddebugging
* Service a minified JavaScript version if `DEBUG=False`
* Add support for the AWS_LOCATION setting
* Increase old browser support and switch to es2015

Officially supported Django versions:

* 1.11 LTS
* 2.2 LTS

Officially supported Python versions:

* Python 3.6
* Python 3.7

* Fix 93 -- Always use POSIX style S3 keys (windows issue)
* Switch to shorter base64 encoded UUID in S3 key

* Add Django 2.1 support (no code change, test suite only)
* Fix 86 -- Catch and log file not found exception