Allow multiple API keys to be used via a filter
Abstract fetching of the API key such that the admin notice doesn't appear when the key is set with a filter.
Pluralize, we support multiple API keys
Pluralize, we support multiple API keys
generate_hashes() should always return an array

See https://github.com/humanmade/WP-Remote-WordPress-Plugin/pull/36#discussion_r4542705
Merge pull request #36 from humanmade/multiple-keys-36

Support for multiple API keys via a filter