Fix class Async() to async_call instead of session.threadsafe_call
Fix class Async() to async_call instead of session.threadsafe_call

python-client master removed vim.session api

Signed-off-by: Koichi Shiraishi <13fbd79c3d390e5d6585a21e11ff5ec1970cff0c@zchee.io>

bfredl/nvim-ipy