added function to stop training

src/Flux.jl

@@ -24,6 +24,7 @@ export SGD, ADAM, ADAMW, AdaMax, Momentum, Nesterov,
        RMSProp, ADAGrad, ADADelta, AMSGrad, NADAM
 
 include("utils.jl")
+# export stop
 include("onehot.jl")
 include("treelike.jl")
 

src/utils.jl

@@ -153,3 +153,9 @@ function jacobian(m,x)
     end
     J'
 end
+
+struct StopException <: Exception end
+
+function stop()
+  throw(StopException)
+end