Avoid service duplication in README (see: https://github.com/toddmotto/public-apis/pull/259#issuecomment-269635584).

https://developer.riotgames.com/docs/api-keys

Removed Hummingbird and updated with the Kitsu api details.

Source: https://medium.com/heykitsu/hummingbird-is-dead-long-live-kitsu-bda6ccfbbcce#.xixj9r30c
https://forums.hummingbird.me/t/kitsu-api-documentation/33367

Add Google Drive API

A section title of "exchange" is a bit vague when searching for a currency API, so add "currency" to the section title to make life, and searching, easier.

re-ordered health section

added diabetes api

Discogs uses/requires OAuth.