Add tox support

- Add a tox ini file
- Add tox.ini to Manifest.in
- Describe tox in docs
- Allow passing arguments to py.test by tox -- py-test-args
- Various additions and configurations to tox.ini
- Add a lot of useful python versions as default envs
- Add skip_missing_interpreters=True as a useful default
- Add two environments for pyflakes and pep8 tests
- Add changedir directives for tests
- Add pytest dependencies
- Improve documentation
rename tox.ini.template to tox_ini.template
Fix typo in tox.ini template docstring
Added Holger Peters as author
ENH: Removed unused import from setup.py
ENH: Added flake8 args to omit certain files
ENH: Added flag for Tox configuration file
DOC: Added some comments to tox.ini
FIX: During update write files that did not exist before
FIX: Python 3 iteritems fix
fix symlink issue on mac os x
Merge pull request #23 from HolgerPeters/develop-bugfix

fix symlink issue on mac os x
FIX: fix shell unittest for MacOS hopefully
ENH: Tox support for PyScaffold
FIX: Travis test for Tox
DOC: Added release notes for 1.3
DOC: Updated features of tox
ENH: Replaced \n by os.linesep
ENH: Better use splitlines instead of os.linesep
FIX: Unittests for last commit