Merge branch 'release/0.6.1' into develop
Return result of recursive snailtrack function
Merge branch 'master' into develop

Conflicts:
	django_snailtracker/models.py
Made mutex multi-server compat

Removed file mutex and moved it to the database using the ObjectLock
model.

Some code cleanup.
stray filesystem code from merge
Addressed concerns commented on the pull request

Changed ObjectLock to have a unique_together option which raises an
IntegrityError if table and object_id (together) already exists in the
database. Removed the key field.

Wrapped the ObjectLock creation in a try/except IntegrityError to
prevent a race-condition from blowing up one thread when two are trying
to lock the same record at the same time.
Merge pull request #1 from aquameta/develop

solid