Upgrade browserify shim to 3.8, resolve unmet peer dependency

Doing a fresh `npm install` of this repository resulted in an error due to an unmet peer dependency as a result of the barrage of package upgrades. `browserify-shim@3.7.x` has a peer dependency of `browserify < 6`. The upgrade to browserify 6 broke on this. shim 3.8 ups the peer dependency to `browserify < 7`.