Updating otindex via github webhooks

Curation activity on the OpenTree website needs to be reflected in the study index. This is the series of events that causes this to happen:

• Users add or edit studies and trees through the OpenTree curation interface
• The web application uses phylesystem-api to push the changes to the appropriate shards of the phylesystem repo on GitHub.
• The push triggers a webhook in the shard (here is an example in the phylesystem-1 shard).
• The webhook calls the (unpublicized) phylesystem-api method http://api.opentreeoflife.org/phylesystem/search/nudgeIndexOnUpdates (code here)
• phylesystem-api passes a list of the study URLs to add, update, or delete to the index
• the index updates the database as necessary