Update .travis.yml.

- Add -v (verbose) flag for debugging purposes
- Use requirements-dev.txt to install Mock
Add mutation support

Add ability to mutate instances via class methods defined on Models.
Add forgotten assignment operator to update keys.
DRY and PUT/PATCH updates

  - DRYer code with some new decorators for instance checking and auth normalization.
  - Support for PUT method for updating entities.
Stylistic fixes.
Add explanation to `Me.read` method override.
Add partial create support.
Merge branch 'mutation-support' of ssh://github.com/BYK/pyresto into mutation-support

Conflicts:
	pyresto/core.py