changes to make tests run on python3
#2 - tox and travis; change to test_configobj to actually fail tox if there are failures

tests actually fail on 26 and 27, but that's another battle
#2 - added validate.py test running to tox.ini
Update README.md
#3 - validate doctest errors correctly fail the build
Merge branch 'master' of github.com:DiffSK/configobj
#3 -asserting types in doctests in a way that's compatible on 26,27 and 3

type(float) says "type" on python 2 and "class" on python 3, which is annoying to doctest
#3 - setting the results of the seek and write methods of file-like objects to a variable to make doctest python 2 and 3 compatible

seek and write return None on python 2 and thus don't print anything in the REPL, but on 3, they both return integer bytes, which does show