Merge pull request #26 from ptal/viboes_interface_change

Minor typos.
Remove useless std::move.
Merge branch 'master' of https://github.com/ptal/Boost.Expected
Uncomment trivial mapping.
Added exception_or.
Added optional_monad alias.
comeback from bind2 to bind.
Cleanup
Merge branch 'master' of https://github.com/ptal/Boost.Expected
Rename bind meta-function to rebind as allocators. fixes #29.
rename next -> mbind in Expected and examples.
Merge.
Format.