Support dynamical loading of LZF filter plugin
Added python 3.4 to tox
Remove 2to3
Make python files 2/3 compatible

The changes are:
 * absolute imports
 * division (/ vs //)
 * use six for unicode/strings, dict.iter*
 * wrapping dict methods in lists where appropriate
Add six to setup_requires as setup.py test does not install install_requires
Fix py32 errors (hopefully got all of them)
Merge pull request #506 from petercolberg/master

Support dynamical loading of LZF filter plugin
Merge pull request #507 from aragilar/test_3.4

Added python 3.4 to tox
Add 'x' mode as an alias for 'w-'.
Merge pull request #510 from anntzer/x-open-mode

Add 'x' mode as an alias for 'w-'.
Don't strip metadata from special dtypes on read.

Fix #511.
Merge pull request #512 from anntzer/roundtrip-special-dtypes

Don't strip metadata from special dtypes on read.
Merge pull request #508 from aragilar/drop_2to3

Drop 2to3, make python files 2/3 compatible.