[web] Use hook instead of connect function and HOC in Day

Summary: Switched to hook instead of the connect function in the Day class.

Test Plan: Made sure that day components still show up in the calander, and that they still function correctly.

Reviewers: ashoat, palys-swm

Reviewed By: ashoat, palys-swm

Subscribers: KatPo, zrebcu411, Adrian, atul, karol-bisztyga

Differential Revision: https://phabricator.ashoat.com/D753