removed comparison with 0

The concept is supposed to generalize pointers and optional<>, but the latter has abandoned the comparison with 0 a long while ago.
Move binary_search_test.cpp into detail module.

The header it's testing is in the detail module, so it should be there.
Merge pull request #9 from danieljames/remove-binary-search-test

Move binary_search_test.cpp into detail module.
Merge branch 'patch-1' of github.com:akrzemi1/utility into akrzemi1-patch-1
Merge branch 'akrzemi1-patch-1' into develop
Remove headers that have been moved into core.
boost::swap, boost::empty_deleter and explicit operator bool macros moved from Boost.Utility to Boost.Core.