3.5.1 Release.

[gavinelder]

Small fixes for a 3.5.1 release to improve usability without a major change for individuals.

Sanitise Keys resolves https://github.com/airbnb/streamalert/issues/1110

Small PR to fix keys which contain special characters.

https://github.com/airbnb/streamalert/pull/1315

GHSL-2021-121 Small regex bug.

It's a trivial item but Github have published a blog post about it so I think this is a worthy security inclusion.

https://github.com/airbnb/streamalert/pull/1325

[ISSUE-1318] Deployment Fails with "ResourceConflictException" in Lambda

https://github.com/airbnb/streamalert/pull/1319

Other notable inclusions.

I can include changes to TF for Deprecations and include 1.X support but I don't think this falls under BugFix