add std::thread call routine and Cancel Method.
thread call but fix.
add static member(bug fix.)
destructor but fix.
indent tab change.
supports multiple calls and thread join.
remove test code.
header bug fix.
change std::thread::id.
Supports multi-thread call.
add example callback_thread.
update Call method.
Revert "update Call method."

This reverts commit fccd40db34d8512b1928f236033075c860d706fa.
Revert "Supports multi-thread call."

This reverts commit f7a182cefde755fcb63dda5ce0e524d92af070f3.
Thread example
Merge branch 'develop' into add-thread
Update libjson-rpc-cpp
Merge pull request #30 from MiLk/add-thread

Add thread