Add tifffile.py by Christoph Gohlke

It's a royal PITA to install [pylibtiff](https://code.google.com/p/pylibtiff/) on recent systems because it a) has to be installed from source under openSUSE (Debian-based systems have python-libtiff packages) and b) it distributes header file specific Python files.

I found the tifffile.py "project" by Christoph Gohlke and according to the license header (looks like MIT license to me) it can be distributed with Concert. So to save us from some pain, I added this module to `concert.ext`. There is one problem though: If I save 32 bit float data, it can be read again and is exactly the same as before saving, however ImageJ displays it wrongly. Maybe you could check that @sensej.