Change triple quotes to parentheses in ascii_str

A multiline string already contains \n

>>> u'''a
... b
... c
... '''
u'a\nb\nc\n'
>>>

It's not obvious that the newline character exists there,
but it is checked.
If some future condition excludes this char, it remains there
due to triple quotes.

The single quote also was escaped in the string.
Merge pull request #10 from code-exchange/triple_quotes_issue

Change triple quotes to parentheses in ascii_str