Fix astropy.wcs import

The WCS module in Astropy is astropy.wcs, not astropy.pywcs
Preferentially use astropy.io.fits and astropy.wcs
Fixed missing astropy import
Use more consistent WCS import for Astropy
Merge pull request #12 from astrofrog/patch-1

Fix astropy.wcs import
add test.header required for demo_print_region.py. closes #13
added .write function to ShapeList
added check for consistent shapes
added versioning code and a version #
added version stuff in setup.py
Fix print statements in demo_print_region.py for Python 3
Declare that pyregion supports Python 3 in setup.py
Update pyfits to astropy.io.fits in test scripts
Add entries to .gitignore
Change to public submodule URL in .gitmodules

This is needed to make pyregion testing on travis-ci.
See travis-ci documentation here:
http://about.travis-ci.org/docs/user/build-configuration/#Use-Public-URLs-For-Submodules
Add .travis.yml for testing on travis-ci.org
uses __builtin__.open
Merge branch 'version' of https://github.com/keflavich/pyregion
workaround matplotlib backward-incompatible change. closes #15.
fix undefined _open_builtin error