replace parse method of etree with ElementTree so that it supports cElementTree also
Revert "replace parse method of etree with ElementTree so that it supports cElementTree also"

This reverts commit 9caad3190330c12dc24306f774850819a1626f77.
corrected init file
add reference to docstring
adds functionality to parse cardinality along with tests refs #123
corrected docstring of Reader class
implemente writing indexes to files refs #123
Merge pull request #127 from ankurankan/dev

replace parse method of etree with ElementTree so that it supports cElementTree also