Added Gitter badge
Merge pull request #1710 from gitter-badger/gitter-badge

Add a Gitter chat badge to readme.md
All unit tests now pass.  Several fixes to both the unit tests and their corresponding classes.
Merge branch 'master' of https://github.com/wp-e-commerce/WP-e-Commerce
Cleanup on delete all customer meta...primarily in that...it did not delete any customer meta
Update Travis to not check 3.8
Ensure we are checking for both empty and non-set values for taxation meta.  Regression from 3.9.1 caused taxes to break.  Fixes #1712.
Merge branch 'master' of https://github.com/wp-e-commerce/WP-e-Commerce