add a spec for setting env vars to other env vars
Export env vars added through the API

We recently added support to add environment variables through the API,
they're sent separately from env vars from config.
Merge pull request #246 from travis-ci/ps-get-env-vars-added-with-api

Export env vars added through the API
Remove duplicate :node
Merge remote-tracking branch 'origin/master' into hh-http-api