Add item label class option for collection inputs.

This allows checkbox and radio collections to be styled with the checkbox-inline and radio-inline styles from boostrap 3 when paired with setting the item wrapper tag to false.
Option fetch is unnecessary for item_label_class
remove warning of label_text method in wrapper, when replace html
label tag to other tag
simply add wrapper_options argument to label_text to avoid warning
Merge pull request #1086 from kaichen/fix-warning-with-custom-labal

remove warning of label_text method in wrapper, when replace html label tag to other tag
Merge pull request #1052 from megahbite/master

Add item label class option for collection inputs.