Fixes for Travis CI builds
Add an optional 'ZKMapListener' to ZooKeeperMap which fires as nodes are added, changed, and removed.
Add tests and changes based on feedback

from 9639406e2cb5d58245c8e839c2ee9295dde3915f
Merge pull request #166 from eric/travis-ci-fixes

Fixes for Travis CI builds
Add null check for listener and other small cleanup
Fix noop listener based on feedback
Fix constructor that was passing null
Merge pull request #165 from eric/zookeeper-map-listener

Update to #11: "Add an optional 'Listener' to ZooKeeperMap which fires as nodes are added, changed, or removed"
Fixup the checkstyle task to skip synthetic targets.

This fixes a regression introduced by changes in a489c3ad to
distinguish codegen targets like java_thrift_library from the
synthetic targets they inject to own generated code.
Merge pull request #169 from jsirois/jsirois/pants/fix_checkstyle_synthetic

Fixup the checkstyle task to skip synthetic targets.
Keep the && chain alive in the travis build, a failed pants build should fail fast.
Cleanups from internal review of ZooKeeperMap(Test)