* Add missing (make build) step for running teleport cluster in docker container
* Edit Dockerfile teleport-buildbox tag from :latest to :go1.13.2 to match the image tag from running "make docker" from root.
* Update root README about docker
This commit introduced mutual TLS authentication
for auth server API server.
Auth server multiplexes HTTP over SSH - existing
protocol and HTTP over TLS - new protocol
on the same listening socket.
Nodes and users authenticate with 2.5.0 Teleport
using TLS mutual TLS except backwards-compatibility
cases.