Add convert implementation for std::tuple

Signed-off-by: Kohei Takahashi <flast@flast.jp>
Add mpl::clear implementation for Boost.Tuple

Signed-off-by: Kohei Takahashi <flast@flast.jp>
Add mpl::clear implementation for std::tuple

Signed-off-by: Kohei Takahashi <flast@flast.jp>
Add test for convert seq to tuple

Signed-off-by: Kohei Takahashi <flast@flast.jp>