Brie/updates sunset

[briemcnally]

What does this PR do?

• [X] Updates the latest Firebase SDK
• [X] Transforms event names to ^[a-zA-Z0-9_]+$
• [X] Transforms property names to ^[a-zA-Z0-9_]+$
• [X] Fix crash when Firebase SDK is instantiated multiple times by not configuring the FIRApp if already done
• [X] Adds unit tests for new functionality
• [X] Adds working CircleCI config

Associated JIRA Tickets: https://segment.atlassian.net/browse/DEST-1085