Merge branch 'develop' of https://github.com/stan-dev/stan into develop
Merge branch 'develop' of https://github.com/stan-dev/stan into develop
Merge branch 'develop' of https://github.com/stan-dev/stan into develop
Merge branch 'develop' into feature/issue-667-fma-calls-fma
removed math::fma function and updated agrad to use ::fma from <cmath>