Refs #50 — WIP
Refs #50 — Write load test.
Add ValueError exceptions.
Verify status_code
@ametaireau review.
Add percentage for random choices.
Add OXMEN timeout.
Leonix is not configured just means that French number will not be using it.
@ametaireau review.
Nexmo MSISDN doesn't have a +
Add response data on failures & fix certificate signature.

r=natim
Add the discover endpoint.
Merge pull request #50 from mozilla-services/50-loadtests

Fix# 50 — Write Loadtests scenario