Performance tweak: don't watch /deploy and /node_modules.

Running a Solidus site inside a Vagrant virtual machine, hosted on a Windows machine is pretty slow (https://github.com/solidusjs/solidus-devbox/issues/6). The problem is with the slow folders sharing between the machines.

This pull request removes unnecessary files from Solidus' watch list, which seems to fix the problem (`node_modules` contains a lot of files, there's no need to watch those).