timestamp INFO [thread name] class-name: message info

java agent start and process when app boot,
it is difficult to use (java.util.logging)JUL correctly 😩;
especially cooperate with app server(eg tomcat or jboss).

use simply std out/error instead of JUL.

more info see #97

more discussion see #95

- 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

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

Improve performance, more info see Alibaba Java Coding Guidelines
Item 12 of Collection section

Merge pull request #87 from lispking/master

- shorten sleep time for speedup test

so anyone can hack ttl without rebuilding ttl from source