Validate swagger as part of CI

[drewish]

A quick hack is to use some bash to send your docs off to the online validator:

bundle exec rake swagger
SWAGGER_LINT=$(curl -X "POST" "http://online.swagger.io/validator/debug" --silent -d @swagger/v2016-09-01/swagger.json)
if [[ $SWAGGER_LINT != "{}" ]]; then 
  echo -e "\nInvalid Swagger:\n$SWAGGER_LINT\n"
  exit 1
fi;