Use UUIDs instead of base64ed random for IDs

Closes #11
Add interfaces to Capture*, rename CapturePanic
Merge pull request #10 from cupcake/refactor-helpers

Refactor capture helpers
Fix method comments
Revert "Use UUIDs instead of base64ed random for IDs"

This reverts commit d72712b5d561af5b6c75e44c69f4ff36f2b3bc8c.

Sentry doesn't want the dashes included.
Format UUIDv4s correctly