Add concurrency torture test for Skiis.merge()
remove(t) should only remove one element
Don't throw exception in Ring.remove(); breaks tests
Eliminate synchronization bottleneck in FlatMapOp
Eliminate (another) synchronization bottleneck in FlatMapOp
Fix concurrency bug in FlatMapOp.next() introduced in commit 8b36ff6 + add better test
Remove build.properties
Merge branch 'master' into bizo-2.9.1

* master:
  Fix concurrency bug in FlatMapOp.next() introduced in commit 8b36ff6 + add better test
  Eliminate (another) synchronization bottleneck in FlatMapOp
  Eliminate synchronization bottleneck in FlatMapOp
  Don't throw exception in Ring.remove(); breaks tests
  remove(t) should only remove one element
  Add concurrency torture test for Skiis.merge()
Add build.properties to gitignore