fixes grammatical errors

doc/library/tensor/nnet/nnet.txt

@@ -120,12 +120,12 @@
 
    The softmax function will, when applied to a matrix, compute the softmax values row-wise.
 
-    :note: this insert a particular op. But this op don't yet
-       implement the Rop for hessian free. If you want that, implement
-       this equivalent code that have the Rop implemented
-       ``exp(x)/exp(x).sum(1, keepdims=True)``. Theano should
+    :note: this uses a particular operation. But this method doesn't yet
+       implement the Row Operation for hessian free. If you want that, you can use
+       this equivalent code that has implemented the Row Operation
+       ``exp(x)/exp(x).sum(1, keepdims=True)``. Theano would
        optimize this by inserting the softmax op itself.  The code of
-       the softmax op is more numeriacaly stable by using this code:
+       the softmax op is more numerically stable because it uses this code:
 
        .. code-block:: python