- https://docs.codecov.io/docs
- https://github.com/codecov/example-java-maven
- https://github.com/codecov/example-kotlin

- build by java 8 with java 6 source/target
    - full functions with java 8 support(ForkJoinPoolTest)
    - support java 6
- Travis ci has multiple java version: java 6/7/8/9
- scripts and test case/demo cleanup

avoid reflect out renamed method unexpectedly

remove releaseTtlValueReferenceAfterCall logic,
because ForkJoinTask cached the run result never actually run twice

- extract method
- rename test class and adjust package

enhance the most frequently used ForkJoinTask:

- RecursiveAction
- RecursiveTask

- update CRR demo code
- remove versioneye badge 😭

add TransmittableThreadLocal.Transmitter, expose internal capture/replay/restore operations for TTL values

1. Transmitter#capture: captures TTL values in current thread
2. Transmitter#replay: replays the captured TTL values after back up
the current ones
3. Transmitter#restore: restores current thread to state before replay

This reverts commit ada90204.
only access key, no need use entrySet #87