Fixed the class name in Simple Usage example.
WKOption class now accepts value as a param while the option is being created.
Removing the WKOption redirect-delay as it is no longer supported by wkhtmltopdf
output_file and url are now looked in kwargs before taking from args

Earlier if the WKHtmlToPdf class' init method was passed both of these params
as a kwarg, the method would fail to find it and just crash!
Now they can be passed either as positional argument or keyword arguments.
We now set option values *only* for those passed as kwargs to WKHtmlToPdf
Merge pull request #7 from knightsamar/compatibility_with_0.12.0

Compatibility with 0.12.0