fix text-fields: use ng-transclude again

Before, we managed the text field directly in the directive template.
It added complexity for binding basic html & angular parameters to the
field (name, ng-focus, etc.). By using "ng-transclude", the user has
entire control over the field. The model and focus state are managed
by the directive without any action by the user needed to apply the
right styles regarding the status.

Close #40 #32
BROKEN:
text-fields must now have their own input or textarea with ng-model