clean up sources
fix issue 10: There is a case that CPU time is nagative
fix Issue 13:ant javadoc fails
fix Issue 11:maxWarmUpTime option for BenchmarkBuilder.run() is not written in its Javadoc
make git to ignore out/
fix Issue 16:The times of benchmarking a closure that does nothing aren't zero
remove debug log
expand the error range
change the version to 0.4.2
fix Issue 17:@Benchmark has same problems with issue 10 and issue 16.
add warmUpTime and maxWarmUpTime system properties
don't warm up when the BenchmarkMeasure is loaded
add test code for BenchmarkContext and clean related code