Goal of this PR is to rework testing script so that actual testing is
easy to extend and perform during development cycle.

* For interoperability testing I use python script and test framework,
  instead of complicated bsah scripts. Script itself is not yet perfect
  but it makes it much easier to extend tests and work with them during
  development time

* Makefile has been extended and now includes all steps needed to build
  the library and run tests. It's now possible to run any kind of tests
  without exporting environment variables.  Thanks to this change it is
  stupid-easy to run any kind of tests.

* There are 3 kinds of tests implemented in the library - unittests,
  interoperability tests and bogo. Travis has been changed and now
  dashbord will show only results for those 3 targets.

Check SupportedVersions for the actual version and verify that the
server sets the correct SeverHello.legacy_version. Change D21 to D22.

D19 added an additional pre-extract Derive-Secret stage. D20 shortened
labels. Bump from D18 to D21 with no backwards compat option for now
since older drafts are considered undeployable.

The default version (TLS 1.2) is no longer overridden with TLS 1.3 so
the server must explicitly set it.

Fixes: ("crypto/tls: allow client to pick TLS 1.3, do not enable it by default.")

This makes it easier to validate the handshake contents using Wireshark.

ConfirmHandshake should block on a Read until the handshakeConfirmed
state is reached, but past that it shouldn't.