Add a pure-go implementation of Zip files

This removes the need for a bash or zip executable, and as a nice side effect,
makes it easier to run the cats on windows
Allow passing flags to 'cf login' and 'cf api'

Useful if you want to skip validating ssl certificates because you're
testing against a boshlite deploy.
Merge pull request #2 from jfoley/flag-zipper

Flag zipper