Add ability to use the HTML5 email input type

Added the ability to use the HTML5 input type Email. It can be enabled by adding the etyp attribute to the shortcode.
If you want to use the input type of EMAIL instead of TEXT, add etyp="1" like this:

\[constantcontactwidget etyp="1" grp="constant contact list name" btn="button text" msg="success message"\]