cereal 1.0.0 (new formula)

Add cereal 1.0.0, a C++11 header-only library for serialization. This
formula includes a "with-tests" option, which can be used to build and
run cereal's internal unit test suite before installation. Note that
these tests are broken for tag 1.0.0, but are not (currently) broken for
the "develop" branch.