DPC : added depreciation warning to BaseFrames
ENH : added class_exts and exts to FramesStream

  - class_exts : classmethod to return the file extensions class
                 can deal with
  - exts : property which just calls class_exts

This is needed for introspection so that dispatching can happen and
for passing up to applications that want to build UI/filter file
lists.

The default interpretation of the file extension set is 'including
but not exclusively'.
PY3K : added six import + __future__ statements to all files

 - patched up py3k issues
CI : added 3.3 to travis config
CI : added six to install list
CI : tweak install to pull python packages from pip, not ubuntu
BUG : fixed un-defined variable in TiffSeries.__init__

  - we need better test coverage
CI : more tweaking of setting up the environment
CLN : fixed up example code so pychecker stopped complaining
CI : update apt-get before installing anything
CI : yet more tweaking of the travis build

 one more round of this and I am giving up and trying conda
CI : trying conda instead

Lifted more-or-less wholesale from
https://github.com/mwaskom/seaborn/blob/master/.travis.yml
at cc0445389aab28432093f35be050f737c9767749
CI : yet more travis tweaking
CI : YARG
Merge pull request #44 from tacaswell/plr_work

Plr work