Fixed PHP Strict warnings.

Child class methods must follow the declarations of the inherited parent
class methods exactly; only __construct() is an exception.
Added classes to front-end form elements to aid themers in styling the output.
Fixed #71: Bump compatibility version to current minor version of WP core; remove patch version.
Merge pull request #74 from Mollom/wp36-php54

Improved PHP 5.4 + WP 3.6 compatibility