Fallback for browsers that do not support the placeholder property.
How to use
The simplest way to create the placeholder is to use the utility method:
This method will check for placeholder support. If it doesn't exist, it will create placeholders for all elements with the placeholder attribute.
You can also create a placeholder for a single input:
#JS new Placeholder('input-id',options);
If needed, the placeholder instance of an element can be accessed through the element's storage under "Placeholder".
className- the class name for the placeholder label
input_class- will be used for the input's class (used for making sure the input's background is transparent)