wrapped max_wait variable in if not exist statement. Enables setting max_wait from /etc/default/sensu script
changed max_wait to SERVICE_MAX_WAIT
Merge pull request #59 from willejs/master

enable setting max_wait from /etc/default/sensu
[max_wait] cleaned up max_wait
Merge pull request #61 from portertech/max_wait

[max_wait] cleaned up max_wait