opener: add read & write utility methods
The two new methods are useful for quickly opening a file for reading
or writing. Unlike 'opener(...).read()', they ensure they the file is
immediately closed without relying on CPython reference counting.
color: verify stdout is a tty before using curses
Without this change, curses complains when invoked in certain contexts
because stdout isn't a tty (such as emacs integration) but we ask it
to check for various bits of information from terminfo.