Documentation typo

[quackenbush]

Hi, I have corrected typos in your last example code.

Old:

from junitparser import Element, Attr, TestSuite

# Create the new element by subclassing Element or one of its child class,
# and add custom attributes to it.
class MyTestCase(TestCase):
    foo = Attr()

Fixed:

from junitparser import TestCase, Attr, JUnitXml

# Create the new element by subclassing Element or one of its child class,
# and add custom attributes to it.
class MyTestCase(TestCase):
    foo = Attr()

[weiwei]

Cool. Thanks!