Update modules.asciidoc

Dear friend:
    I found that 'dir('print')' in Python 3.4 will get the same output as 'dir(str)'. 'dir(print)', however, works well.
Update problem_solving.asciidoc
Update oop.asciidoc
Update io.asciidoc
Merge pull request #13 from myd7349/master

Some small fixes