feat text-fields: add textarea in text fields components

The text area can be used with a type of "area". The text area's
height grow with the content.
chore demo: text fields demo updated with textarea
feat text-fields: fixing padding

Before the border position under textarea was wrong. It is now fixed,
the space is a little bigger between the textarea and the border.
Chore demo: demo updated with good position for textarea border
refactor text field: textarea refactor

Update fields line height to be more consistant through inputs and
textareas.
Refactor textarea to remove useles copy.
Fix model watcher.
Merge pull request #36 from lumapps/feat/textarea

Feat/textarea: add textarea in text fields components