Snowplow Python Tracker v0.8.3

Fixes a few bugs & updates internals of the project

Bugs

• Fix test_bytelimit test (#227)
• Initialize Celery in CeleryEmitter (#226) by @juliomenendez

Updates

• Allow non ascii characters to be encoded using Base64 (#194) by @jackwilliamson
• Allow empty strings in string_or_none contract (#184) by @joshblum
• Fix on_failure param docstring description (#225) by @mark-walle
• Bump max version requirement of redis (#223) by @akachanov
• Remove Vagrant & Ansible (#222)

Run pip install snowplow-tracker==0.8.3 to get started with!