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

This allows this xblock being hooked into get_course_lti_endpoints for
discovering LTI result/outcome endpoints.

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

Use django.utils.timezone.now() when determining if the due date of a component has passed to avoid tz-aware/naive datetime comparison bug