Remove leftover debug statement.
Whitespace.
Add a module docstring.
Add and edit some function docstrings.
Move validate to the bottom...

in preparation for adding another public function.
Tweak one more docstring.
Split out a `validate_dim_data` function.
Add validate_dim_data to the module docstring.
Merge pull request #86 from enthought/feature/validator-cosmetics

Validator cosmetics