- simplify isEmail() regex (only checks for @); fixes ReDos vuln.
- add support for asynchronous custom validators/filters
- cast to string for string-specific filters to prevent errors
- use express 3.x for peer and dev dependencies
- use express 2.x as peer dependency
- add express 3.x support
- add express as peer dependency
- add isDate validator
- upgrade validator module to 0.4.x