Create a variable

curl "https://api.phrase.com/v2/projects/:project_id/variables" \
  -u USERNAME_OR_ACCESS_TOKEN \
  -X POST \
  -d '{"name":"MY_VARIABLE","value":"Hello World"}' \
  -H 'Content-Type: application/json'

{
  "name": "MY_VARIABLE",
  "value": "Hello World",
  "created_at": "2015-01-28T09:52:53Z",
  "updated_at": "2015-01-28T09:52:53Z"
}