Arbitrary websocket headers

Tidy develop branch

also separate out the header joining into a function

http://pytest.org/dev/yieldfixture.html

    With pytest fixture functions, the “after yield” part will always be invoked, independently from the exception status of the test function which uses the fixture.

Use socketserver to make a temporary server which websocket tests can be run against, which takes data to return.

Probably needs extending so more checking can be done on the path etc.

Signed-off-by: NJames Myatt <james@jamesmyatt.co.uk>

Note that MQTT v5 also uses protocol name = "MQTT"
Signed-off-by: NJames Myatt <james@jamesmyatt.co.uk>

Signed-off-by: NJames Myatt <james@jamesmyatt.co.uk>

Signed-off-by: NJames Myatt <james@jamesmyatt.co.uk>

Now contains a more full example of how to connect to AWS IoT platform and points to it in the documentation.

Client was stopped too early, not allowing it to always close
the connection which cause timeout in this case.

Make auth dict handling a bit more leniant

Use mutexes as context managers

Use tox to run tests

Signed-off-by: NJames Myatt <james@jamesmyatt.co.uk>

Fix for bug #3