Fix #270 (#274)

* Fix #270

* fix fma(dual,real,dual) tag

* add TestTag() to Duals in DualTest

* Make dual_isapprox throw errors when tags are different

Author: ChrisRackauckas

src/dual.jl

@@ -465,7 +465,7 @@ end
     return quote
         $(Expr(:meta, :inline))
         v = fma(value(x), y, value(z))
-        Dual(v, $ex)
+        Dual{T}(v, $ex)
     end
 end
 
@@ -507,7 +507,7 @@ end
     return quote
         $(Expr(:meta, :inline))
         v = muladd(value(x), y, value(z))
-        Dual(v, $ex)
+        Dual{T}(v, $ex)
     end
 end