Merge release v1.3.1

Ping @ewindisch @unclejack @crosbymichael @jfrazelle @LK4D4 @vieux 
Please make sure all 1.3.1 commits from the release branch are here, or on master.
@thaJeztah yes, sorry but this is not the PR to discuss this. Feel free to open a PR to fix documentation once this is in master.