Add a separate config option for s2s auth token endpoint

In some cases the auth token endpoint for service to service calls is
different from the normal WAAD login one
Create tables on startup rather than on first request

Otherwise we get problems running the tests for the first time and
calling `reset_db()`, as the table is present in the metadata but not
actually present in the DB. This causes issues like:

ProgrammingError: (ProgrammingError) relation "service_to_service_access_token" does not exist
LINE 1: delete from "service_to_service_access_token"
                    ^
 'delete from "service_to_service_access_token"' {}
Tweak BeautifulSoup test to make it work on older versions
Set up Travis
Fix base paths
Merge branch 'travis'
Add Travis widget