This issue is to add a str class entry to the built-in types page like we have for dict, set, memoryview, etc:

http://docs.python.org/dev/library/stdtypes.html

This will let us reference ``str`` the class separately from ``str()`` the built-in function.  It will also let us remove the "str." prefix from all of the string method descriptions.  Thirdly, it will make the str documentation match what is being done for the types previous to it in the documentation, including the range, tuple, and list classes.  Lastly, it will make referencing string-related sections in Sphinx a bit more intuitive.  Currently, :class:`str` points to the built-in function :func:`str`.