Starting to implement N3960
More work on foreach, started to add tests, non-functional, still
for_each functional
Fix return type handling for for_each
Adding missing file
Adding more tests, handle exceptions
Adding tests for for_each_n
Adding transform, started to work on tests
Fixing exception handling, adding more transform  test
Merge remote-tracking branch 'upstream/master' into n3960
Adding transform_binary tests, fixing other tests
Removing old for_each
Made execution policy selection more pretty
Properly handling sequential execution policy
More test fixes
Adding constexpr in some places, fixing for_each_n and corresponding test
Added special handling for bad_alloc as mandated by the proposal
Tweaking for_each
Adding new 1d stencil example using parallel::for_each
Merge remote-tracking branch 'upstream/n3960' into n3960