add a test to test a job's lifecycle.
Fix handling of close events.
Move `save job` functionality of pulsar.createJob to a separate method pulsar._saveJob.
Update docu of `Pulsar`.
Refactor `Pulsar`. Move private methods to the end of file.
Optimize `Pulsar.getJob`.
Update docu of `PulsarDB`.
Merge pull request #49 from vogdb/issue-49

Update job's data on `close` event.