v4.0-beta.2.1

This is just a small release. It includes fixes for excel theme, compression of jquery.flot.js and a fix for the history plugin.

Major Changes

• Use latest image optimizations to reduce bytes over the network by @anthonyryan1 in #2355
• move httprpc response methods to js/rtorrent.js and add jest tests by @TrimmingFool in #2356

Full Changelog: v4.0-beta.2...v4.0-beta.3