Reduce battery usage by using exp backoff on connections (Bryan Montz)

Merge branch 'master' into exp-backoff (Bryan Montz)

add unit tests for RelayPool (Bryan Montz)

refinements to RelayConnection and RelayPool (Bryan Montz)

fix build (Bryan Montz)

apply exponential backoff to retrying stale relay connections to reduce energy use (Bryan Montz)

pushed to refs/heads/master