Fixed context issues for 2.5; dbxml issues for 2.4
Adding some backwards compatibility with 2.4.x
Added AwaitingSourceAcquisitionMessage to dict
Docs
Moodle 2.8's LTI module uses a different method to get custom params
More dictionary entries
Pull dictionary dynamically from TADC
Add hmac signature to dictionary request
Wrong attribute name
Apparently the dictionary isn't always require/include_once'd
Migrate to preg_replace_callback for this
Merge pull request #4 from talis/2.5-compatibility

2.5.x and 2.4.x compatibility