Remove redundant allow.

I originally thought this was required to allow use of the
`have_received` matcher, but not sure what I was thinking.
Merge pull request #725 from rspec/spec-fix

Remove redundant allow.
Preserve null objectness when copying test doubles.

Fixes #732.
Merge pull request #733 from rspec/copy-null-objectness-on-dup-and-clone

Preserve null objectness when copying test doubles.
attempt to reword docs
Merge pull request #738 from rspec/reword_dynamic_classes_docs

Improve documentation for dynamic classes.
Don't inadvertently define BasicObject
Merge pull request #739 from cgriego/master

Don't inadvertently define BasicObject
changelog for #739
Allow matchers to be used in place of keyword arguments in `with` expectations.