Added ``is_caret_in``.

The function ``wait_for_caret_to_be_in`` was split to have
``is_caret_in`` to just check whether the caret is in an element.
Added ``paste``.
Added methods to select text directly.
``select_text`` now supports a ``no_selection`` argument.
Support WEDUTIL_SKIP_OSX_CHECK.

If the WEDUTIL_SKIP_OSX_CHECK environment variable is set, the check
for OS X is skipped.
Rigmarole needed at least up to 2.42.1.