Ensure to generate input_class only for the input, not for the wrapper

Thanks @ollym for catching this one. Related to #337.

Conflicts:
	CHANGELOG.md
Merge pull request #622 from stephenprater/classes_on_use

add html classes to inputs with the wrappers API

Conflicts:
	lib/simple_form/wrappers/builder.rb
	test/support/misc_helpers.rb
Remove unneeded instance variable
Extract a private method to apply the label_input component options
Reverse merge to be consistent with defaults
Consistent usage of setting component attributes through the wrapper api: mostly merging issues