I grepped the documentation in the cpython repository and replaced all mentions of "member(s)" with "attribute(s)" where I felt appropriate.  I left mentions of "members" related to structs or any C documentation alone as I'm less confident of their terminology (I'm new around here).

I used "methods and attribute" in io.rst because BufferedIOBase included one attribute and several methods.  My terminology may be off, but I felt this was the correct replacement of "members."

Please review the patch and critique it as necessary.