added failing NaN test for agrad/rev/fmax
fixed agrad/rev/fmax so gradients return NaN when input is NaN
added failing nan test for agrad/fwd/fmax
fixed agrad/fwd/fmax so derivatives return nan for nan input
added doc for fmax
Merge branch 'develop' into feature/test-nan-fmax
added NaN test for as_bool
added NaN test for as_bool
added doc for as_bool in code for NaN input
Merge branch 'develop' into feature/test-nan-as-bool
Merge branch 'develop' into feature/test-nan-hypot
switched to no namespace version of hypot
cherry-pick  bc17118d99d89bd51b576661ddb8c697b4de0cdd
added NaN test for hypot
added doc for hypot
added NaN test for ibeta
added doc in code for ibeta
Merge branch 'develop' into feature/test-nan-ibeta
Merge branch 'develop' into feature/test-nan-op-gte
add NaN test for operator_greater_than_or_equal