Version Bump v3.2.2: Added TOC and USE_CASES.md

Version Bump v3.2.1: pep8, PyPi fixes

Correcting version number

Version v3.1.10: Fix botched 3.1.9 release

Update TROUBLESHOOTING.md

Version Bump v3.1.8: Added a troubleshooting section

Versiom Bump v3.1.7: Issue sendgrid#195 The variable apikey and api_k…

…ey are now interchangeable

Version Bump v3.07: README documentation improvements

Version Bump v3.0.6: Update docs, unit tests and examples to include …

…Sender ID

Merge pull request sendgrid#190 from sendgrid/189-disable-open-click-…

…tracking-response

Fix for issue 189