merge
refactoring fvar
refactor fvar; runs all fvar tests
refactor abs in fvar
refactor acos in fvar
refactor acosh in fvar
refactor asin in fvar
refactor asinh in fvar
refactor atan in fvar
refactor atan2 in fvar
refactor atanh in fvar
refactor binary_log_loss in fvar
refactor binomial coeff log in fvar
refactor cbrt in fvar
refactor ceil in fvar
refactor cos in fvar
refactor cosh in fvar
refactor erf in fvar
refactor erfc in fvar
refactor exp in fvar