Merge pull request #1 from raistlin7447/master

Timezone issues
Fixed and refactored unittests. Updated naming in docs.
Added fields for a custom email for monitor errors and monitor
description.
Updated safety of monitor description.
Fixed migration default and corrected error email usage of monitor
template.
Added ability to auto-delete old log records.
Added admin actions to more easily enable/disable selections of jobs.
Expanded README docs.
Improved support for inter-job dependencies. Fixed issues with possible
race conditions.
Added list filter by is_monitor to job model admin.
Fixed bug in cron command causing disconnect error from MySQL.
Added use of PID lock file to ensure cron management command cannot have
overlapping executions.
Fixed bug settings last_run timestamp for new models. Fixed URL used for
boolean icons.
Fixed formatting errors in README.
Added check for missing object, per #5.
Updated description.
Updated version.
Fixed error handling in admin field. Added option to disable
select_for_update.
Added option to enable/disable job lock file, fixing major bug in
multi-host configurations. Fixed admin field throwing error when no
next_run set. Fixed error thrown by timezone conflict with dateutils.
Fixed encoding error in job log.
Fixed error saving log string.