Merge pull request #33 from hhoffstaette/master

Data file leaks lead to test failures.
Improved journal close, both sequentially and concurrently, with all journal operations throwing a dedicated exception when called after close.
Fixed leaky file removal on compaction by also closing the associated random access files.
Improved delete performance by:
- Checking with inflight writes and only syncing them when needed.
- Reduced number of seeks.
- Only physically syncing when the corresponding journal property is set.