Add null check to ThreadPoolExecutorMBean
Update dense hll spec to reflect latest code
Update dense hll diagram
Allow specification of the time unit of TimeStat

TimeStat allows the time unit to be specified when adding a sample to the
distribution but when queried returns data implicitely converted to seconds.
This diff allows the time unit to be specified when a TimeStat is created
causing the returned data to be converted to the given unit.
Fix typo
Formatting
Fix inadvertent masking of errors when detecting jmx agent

The old code was catching *all* exceptions thrown by the code that detects whether
the jmx agent is already running in the VM, including errors that were intended
to be propagated to the caller.
Add convenience constructor to TimeStat
Update NEWS and CHANGES
Update to airbase 21
[maven-release-plugin] prepare release 0.89
[maven-release-plugin] prepare for next development iteration
Add abstract event client class
Update NEWS and CHANGES
[maven-release-plugin] prepare release 0.90
[maven-release-plugin] prepare for next development iteration
Do not include dependencies from zip files in lib dir

Zip files are not code and should not be included in the lib dir of an
assembly.  Also, transitive dependencies from zip files should not be
considered.
Update NEWS and CHANGES
[maven-release-plugin] prepare release 0.91
[maven-release-plugin] prepare for next development iteration