Move disabling of autocomplete from HTML to JavaScript

I'm not sure if this matters to anyone or not.  I thought it might be a good idea to remove the hard-coded autocomplete attribute from the form element and add it with JavaScript instead.  There no point disabling a browser feature unnecessarily since it's only required when JS is enabled.  Autocomplete is also a non-standard attribute prior to HTML5 so this could prevent validation if someone expands this project to work on pre-existing forms (as a jQuery plugin, for instance).
This could also be moved to stepForms.js but I left it here for simplicity.