Does not switch outer quotes to avoid escaping quotes

[peterjc]

Consider these examples:

print('Peter\'s favourite programming language is Python!')
print("Using \"Quotes within quotes\" is a pain.")

The PEP8 recommendation is to avoid escaping quotes when you can wrap a string with the other kind of quotes, thus I would expect this output (regardless of which quotes are preferred):

print("Peter's favourite programming language is Python!")
print('Using "Quotes within quotes" is a pain.')

Currently unify does not alter these lines.