HOTFIX: disable pushing stats to Coveralls

Seems to be broken atm.
Refactor: pass sandbox path and root path to provisioner

And remove common functions shared by all provisioners.
Refactor: rename CreateSandbox to PrepareFiles

And get rid of CleanupSandbox, which wasn't used anyway.
Refactor: decouple provisioning from resolving cookbooks
Refactor: decouple provisioning from installing Chef
Refactor: restore original order of actions
Refactor: create sandbox outside of provisioner
Refactor: consistent naming/logging
Merge pull request #39 from mlafeldt/big-refactor

Decouple provisioner from resolver and installer
Goodbye, Coveralls

The service is flaky and I've never used the coverage stats anyway.
Merge pull request #41 from mlafeldt/goodbye-coveralls

Goodbye, Coveralls
Travis: test against Go 1.4
Travis: enable Docker builds

http://blog.travis-ci.com/2014-12-17-faster-builds-with-container-based-infrastructure/
Install cover tool from new location