[docs] Provide some examples for usage of ElementTree methods/attributes (issue 15586)

[eliben at gmail.com]

http://bugs.python.org/review/15586/diff/5726/Doc/library/xml.etree.elementtree.rst
File Doc/library/xml.etree.elementtree.rst (right):

http://bugs.python.org/review/15586/diff/5726/Doc/library/xml.etree.elementtree.rst#newcode102
Doc/library/xml.etree.elementtree.rst:102: import xml.etree.ElementTree
as ET
Please fix this similarly to my fix for the 3.3 patch

The parse method you call returns an element, not a tree, and anyway
there's a shorter way (ET.parse function)

http://bugs.python.org/review/15586/diff/5726/Doc/library/xml.etree.elementtree.rst#newcode111
Doc/library/xml.etree.elementtree.rst:111: :func:`fromstring` parses XML
from a string directly into an :class:`Element`,
Please also align here for the fixed 3.3 patch

http://bugs.python.org/review/15586/