finagle: Update ADOPTERS.md
finagle: Update ADOPTERS.md

Summary: Problem / Solution
Add Hotels.com to Finagle adopters.

Signed-off-by: Ryan O'Neill <ryano@twitter.com>

JIRA Issues: CSL-5071

Differential Revision: https://phabricator.twitter.biz/D81561

mkhq/finagle,mkhq/finagle,twitter/finagle,twitter/finagle,twitter/finagle,luciferous/finagle,mkhq/finagle,luciferous/finagle,luciferous/finagle,mkhq/finagle,mkhq/finagle,luciferous/finagle,twitter/finagle,luciferous/finagle,luciferous/finagle,twitter/finagle,mkhq/finagle