Add python etree support.
Merge branch 'master' of github.com:atztogo/phonopy
Support for using Python's default cElementTree without using lxml.
Refactoring iterparse.
Minor updates.
More simplifications.
Make naming more consistent.
Merge branch 'master' of https://github.com/materialsvirtuallab/phonopy into merge-shyue
Propagated modifications by shyuep's commit