feat(client/deis): add python3 support

Changes:
- use python future for single source
- change octals to new style of `0oXXX`
- add `future==0.14.1` as dependency

Breaking Changes:
- `future==0.14.1` requires python >= 2.6
Would the fix for the job be `from __future__`, perhaps? I've seen that from place to place. Sorry if this seems noobish, I'm not too familiar with making clients python2 and python3 compatible :)