Bumping the max_length for the field_class to allow adding longer class names.  I ran into trouble when trying to add a phone number field form with a class name of "phonenumber_field.formfields.PhoneNumberField" (which is longer than the current 32 char max) to the FIELD_CLASSES used in the combo box for adding a new form field.
Merge pull request #70 from daveLonghouse/master

Bumping the max_length for the field_class to allow adding longer class ...