updated paths to reflect new dir structure
new definition of train broke line 31, commented for now
added type requirement for autodiff

produces a more graceful error when forwarddiff_derivative is called on
something other than a Float64
more compact creation of actd
NNLayer: added element-wise exponentiation

to be used for adagrad training
fixed a mistake
outdated comment removed
No need for paths; import the library
Import now works
& put NNLayer and MLP into their proper location