Query experiment


    $ curl "localhost:8080/increment?expId=999&armId=AAA&offers=1"
    OK
    $ curl "localhost:8080/increment?expId=999&armId=BBB&offers=1"
    OK
    $ curl "localhost:8080/increment?expId=999&armId=BBB&rewards=1"
    OK
    $ curl "localhost:8080/query?expId=999"
    {"errors":[],"results":[{"rewards":1,"offers":1,"armId":"BBB"},{"rewards":0,"offers":1,"armId":"AAA"}]}

This uses persistent storage to a directory named "activate" by default. Perhaps we should name it something like "bandito_prevayler_db"