Updated to latest from https://github.com/jleyva/moodle-local_ltiprovider
refactored ims-blti/OAuthBody.php to use CUrl instead of FOpen.  CUrl's
error reporting is much more easy to deal with, and Moodle requires CUrl
anyway.
refactored lib.php to be able to more sanely be able to cope with
returning a single grade, instead of separating it into another file.
Minor refactor of grade_on_demand.php.