Added convenience functions
@bih Made numerous improvements:
Added a SCLAlertViewResponder class that allows the use of .Close(), .setTitle(String) and .setSubTitle(String) upon instantiating a new SCLAlertView.
Added convenience functions for each style of alert. Such as SCLAlertView().showSuccess(self, title: "", subTitle: "") which is purely for readability. Assumes 2.0 duration.
Added the option in .showTitle() to change the 'Done' button to whatever you wish under the completeText attribute. It is optional and defaults to the original 'Done'.
Updated README to reflect new changes and polished up a few mistakes. Also cleaned up the code to look slightly more readable and syntactically beautiful.