XHR request and response #6

- optionally return html strings as json messages on xhr requests
- fix validateif validation
- add noMatch field attr messages
- fix example validateif ref
Errors as html when header set #8

- look for 'x-errors-as-html': 'enabled' to return errors as html
form.js modification

- remove unneccessary array length check
Merge pull request #7 from JoeChapman/feature/xhr-error-response

XHR request and response #6