Updated mock form elements

Added setValue and getValue to TextField, TextArea, Switch, SearchBar,
and Slider views that fire the 'changed' event on setValue.
Added $.val()
Removed duplicate text? check
Added support for attribute selectors
Restore require('tb').load() method of loading tb

This allows override of stickit in addition to other future extensions.
Minor text change to view test
Added support for backbone.stickit

Closes #18.