add random sample endpoint #103
Description
Notes from @philbudne:
The search/sample endpoint, but there isn't currently a method in mediacloud.api.SearchApi for it. The endpoint returns all fields (except the full text, although the recently added underlying mc-providers random_sample method requires a list of fields to return (the words method uses this to select just title and language). The maximum sample size is 10K / field-count, which allows 5K stories to be retrieved for words, which means the max limit for the 8 fields returned should be 1250). 10K is an ES limit on how many documents can be retrieved without pagination.