tox: py33→py34
Implement alternative rules (#16)

To be done:
1) fix the one_of() helper to support OneOf node;
2) fix all FIXMEs;
3) check coverage.
Fix Python 2.6
Depreek of deputrefation
Use repr() in InvalidKey message
Fix merging defaults for a list with OneOf
I mean, really fix it
Introduce a common base for Rule and OneOf, add tests
Fix test for Py3
Support OneOf schema node in one_of shortcut
Merge pull request #18 from neithere/16-alternative-rules

Alternative rules (OneOf)