2018-05-09 version 3.0.0

<< breaking changes >>

• Change offset parameter updating rule. If parse error is happend, offset is updated to the error position. (#639, #666)

<< other updates >>

• Improve cross platform configuration (#655, #677)
• Improve build system (#647)
• Improve user class adaptor (#645, #673)
• Improve msgpack::object visitation logic (#676)
• Remove some warnings (#641, 659)
• Add -> and * operators to object_handle (#635)
• Improve CI environment (#631, #634, #643, #657, #662, #668)
• Improve documents (#630, #661)
• Refactoring (#670)
• Add OSS-Fuzz support (#672, #674, #675, #678)