message: Fix typos in low-level introduction documentation
  Remove extraneous comma.
  Capitalize 'Loss' title.
  Add missing space to 'minimize the'.
diff: @@ -295,7 +295,7 @@ the same input. @{tf.layers$Layers} are the preferred way to add trainable
  parameters to a graph.
  Layers package together both the variables and the operations that act
  -on them, . For example a
  +on them. For example a
  [densely-connected layer](https://developers.google.com/machine-learning/glossary/#fully_connected_layer)
  performs a weighted sum across all inputs
  for each output and applies an optional
  @@ -478,7 +478,7 @@ good. Here's what we got; your own output will almost certainly differ:
  [ 0.10527515]]
  ```
  -### loss
  +### Loss
  To optimize a model, you first need to define the loss. We'll use the mean
  square error, a standard loss for regression problems.
  