Have _acquire_specific_tag also acquire tags directly from the list of free tags (rather than the free set) to avoid the possiblity of a situation where _acquire_tag grabs a tag from the head of the free list and _acquire_specific_tag acquires the same tag from the free set).
Store who acquired a tag and why when tags are acquired (and remove the information when tags are released).
Move inuse tags to alongside other public methods.
Add acquired_by() and owned_by() methods for retrieving information about who acquired a tag and what tags an owner has acquired.
Merge branch 'develop' into feature/issue-500-add-ownership-to-tagpool-manager
Renamed owned_by to owned_tags for consistency with other tag listing methods.
Add tests for using unicode tags and owners with owned_tags.
Fix calling acquired_by on un-acquired / un-declared tags.
Add length option to Lists.
Add acquired_by and owned_tags methods to tagpool API.
Fix handling of default arguments and add test for them.
Add owner and reason parameters to aqcuire_tag and aqcuire_specific_tag API methods.
Add tests for owner and reason arguments to acquire_tag and acquire_specific_tag API methods.
Merge branch 'feature/issue-500-add-ownership-to-tagpool-manager' into develop
Merge branch 'develop' of github.com:praekelt/vumi into develop