Add context_label and context_title to LTI POST parameters; Add required requirements; add some docker devstack instructions;

The module used for rebind was set to LtiConsumer instead of the xblock,
which is wrong and causing an silent exception thrown and return 404 to
the client without any indication of the cause.

Updating code to look at UserProfile.language_proficiencies; updating tests; iterating version to 1.0.8