v1.3.11

Documentation

Added docs which describe the Claimant Model of transparency, a useful
framework for reasoning about the design and architecture of transparent
systems.

Misc improvements

• Fixed int to string conversion warnings for golang 1.15
• Metric improvements for fetched leaf counts
• Move tools.go into its own directory to help with dependencies

Dependency updates

• go-grpc-middleware from 1.2.0 to 1.2.2 (#2219, #2229)
• stackdriver from 0.13.2 to 0.13.4 (#2220, #2223)
• Google api from 0.28.0 to 0.29.0 (#2193)