Add support for dynamic widget attributes

Sometimes it is desirable to set widget attributes after the form is
created. This makes it possible and should be fully backwards
compatible.
Merge pull request #80 from path/dynamic-widget-attributes

Add support for dynamic widget attributes
v0.3.0
Upgrading browserify.
Adding a "required" validator.
When the "required" option is true, use the default "required" validator. Otherwise, use the passed-in validator.
Use String() instead of the toString prototype method.
Merge branch 'required_validator'. Closes #81.
Updating browserify.
Updating browserify.
Adding npm badge and version svg.
Rearranging badges
Unset strict SSL for node 0.6 in Travis-CI
Test in node 0.11 too
submit buttons are so much better than submit inputs.
Pass the method into the example template.
HTML attributes should be double quoted.
Use formidable to handle multipart-encoded form data.
Make the complex example use POST and be multipart-encoded.
Made label text for camel case or dash separated field names format nicely.