CI/WIP: Use conda for most deps

closes #6870 

- [x] use conda.binstar.org/cpcloud channel for versions/packages not in conda defaults
- [x] possibly bring back the ccache, not totally sure what this is doing

this doesn't remove maintenance, but it sure does simplify things, since conda recipes are very easy to create
This was changed to 0.7.4 in the meantime (reason for the test failures)