Merge pull request #1 from jeroen/master

derp
Update to version 4.0

   Where there is a file upload, now file_required and required force the user to upload a file.
   Added image icon mimes.
   Added valid_date method that checks if a field has a valid date format.
   Added valid_range_date method that checks if a field has a valid range of two dates.
Field error message changes

Now the error field message shows all the error messages that it has and not only the first one.
Update MY_Form_validation.php
Update MY_Form_validation.php
Merge pull request #2 from Patroklo/master

Versioin 3.2, 4.0 and 4.1