Produce useful errors with stack traces
Change read/command to command/2/3

Read is deprecated in favor of command/2/3 that now always returns a
return value per actor. In this way, the old read and command can be
implemented on top of the new command implementation.

Note: the error `actor_not_active` is no longer possible to get, instead
you will only get an empty list back from command/2/3 if there are no
actors.
Merge pull request #3 from eproxus/merge-read-command

Change read/command to command/2/3
Bugfix: Channel lock extend was never called.
Add save_timeout.
All actors are periodically saved with this interval.
Bugfix: channel timeout tried to update wrong key in locker
and didn't check return value.
Cleanup actor locks if channel crashes in init/1.
Spelling and better comments on weird code
Optional actor callback should_save/2 to determine if the
actor should be written to the db.
Send init_args to from_struct instead of db representation of key.
Bugfix: correct return value and error log message when channel fails to start
Merge branch 'master' into init_args_to_from_struct
Make lease times configurable in for locker
Merge branch 'master' into init_args_to_from_struct
Bugfix: wrong config name
Merge branch 'master' into init_args_to_from_struct
wes_actor:dirty_db_val/1 debug function
Merge branch 'master' into init_args_to_from_struct
Use wooga's fork of s3erl

Knutin's master functionality has been merged there.
Use latest locker