Replace global mixin GlobalHelper

- Extract its parts into TestZip and TestConfig
- Explicit receivers make it much easier to find method usage and definition

Signed-off-by: Abhijit Hiremagalur <abhi@pivotallabs.com>
Avoid more widely-scoped mixins

- Also organize files in spec/support since there are getting to be quite a few things in here
- We are trying to avoid mixins in favor of explicit receivers to make usage more transparent

Signed-off-by: Abhijit Hiremagalur <abhi@pivotallabs.com>