try python 3
use modern Exception "as" for python3 support
change 0750 to 0o750 for python3 support
update doc for python 3 support
announcing that package works with Python 3
Merge branch 'python3' of https://github.com/grigouze/gandi.cli into grigouze-python3

Conflicts:
	gandi/cli/core/utils/unixpipe.py
Add python3 support (merged pull request #19 from grigouze/master)