Handle 401 errors on /account
bump excon, adapt the HerokuAPI interface to work on newer version

the code in there parsing the heroku_api_url and extracting values
to pass to super is actually borrowed from Excon.new
do not allow http calls on tests
update test for new excon; this actually makes more sense
rewrite original patch to use an exception instead of res.status
Merge pull request #110 from heroku/pedro-handle-401-on-account

Handle 401 errors on /account