Added deprecation warning for tag name

Add deprecation warnings for class name, tag name locator strategies.

Deprecations warnings will now be thrown for:
* 'tag name' in the native context
* 'class name' in the native context
* 'class name' in the web context

'class_name' is now a valid locator strategy for checkValidLocStrat
Change class_name to class name, to match JSONWP