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

Merge pull request #68 from wuwen5/fix-java8-lambda

Utility classes should not have public constructors

- update fuction description of README
- add toc of README
- link to javadoc 7 instead of javadoc 6

- update code and doc: concept multi-thread context(MTC) => TTL
- package mtc => ttl
- update word 'context' to 'TTL value'

- add throws javadoc
- more description about idempotency
- explicit describe that return null when input is null