Fix locks (I think).

I was getting into a condition (Java 7 on OS X) where the writeLock vs readLock were conflicting. The holder of the writeLock was semi-busy-looping, waiting for the `writeCache` to empty, but never released the lock (or awaited a condition) before entering that loop.
Merge pull request #49 from csm/master

Locking fixes (I think)
Improve site and build file
Improve secondary keys
Fixed Issue #50, BTreeMap submap errors
Fixed Issue #36, disk leak in StorageJournaled
Add compaction, fix Issue #18
Merge branch 'master' of github.com:jankotek/MapDB