add grape
add grape-entity
add orders api
api key generation
add APIToken model
authenticate api by HMAC matching
combine api params to payload
refactor authenticator spec
add tonce to api authenticator
set current user on success authentication
api error handling
upgrade grape and grape-entity
orders api require authentication
validate params of orders api
refactor api exception handling
disable HEAD and OPTIONS on api
do NO cascade
order api presentation
fix routes order
add tickers api