Use the Zendesk API to update a user's email
Move .env to .env.sample
add slides as a dep

it's a dependency of rack-instruments, but since we call it directly, it
should be listed in the Gemfile
new user update logic, use v2 API
delete commented code
`run` the Web module so that 404s are handled somewhere
fix issues with API calls as they stand

Fixed:
* SSO calls return 302, not 200
* Excon doesnt decode URL components for basic auth
* search returns results in a 'users' hash

Still broken:
* The current PUT call to update the user's email has no effect
update email address: create new identity, delete old one
make new identity primary & verified
merge branch 'brandur-update-user-api' (PR #2)