Allow registry to be explicitly set

• I am on the latest Hyper.app version

• I have searched the issues of this repo and believe that this is not a duplicate

• OS version and name: macOS 10.14.1

• Hyper.app version: 2.0.0

• Link of a Gist with the contents of your .hyper.js: n/a

• Relevant information from devtools (CMD+ALT+I on macOS, CTRL+SHIFT+I elsewhere): n/a

• The issue is reproducible in vanilla Hyper.app: n/a

Issue

Feature Request: Allow the registry URL to be explicitly set for Hyper

Currently, the registry URL only uses what is in the global .npmrc. Because I work on a corporate machine I use a VPN in order to access our company's internal NPM repository. But, when I'm not on VPN, Hyper will show me an error that it cannot update plugins.

The best way I see to solve this issue is to let a user create a configuration setting in the .hyper.js file for registryUrl.

registryUrl: 'https://registry.npmjs.org'

With this change Hyper would let users bypass any .npmrc settings, especially if they have problems connecting to a custom registry but still want their plugins to update.

Start with the .hyper.js configuration and the existing plugin-update path that reads the global .npmrc. Trace how the registry URL is selected, then verify that a registryUrl setting can override .npmrc and allow plugin updates with or without the corporate VPN.