Enable isGlobal setting

[jensmeindertsma]

The update message by update-notifier was telling me to run npm install npm-check-updates, and without looking carefully I did just that, and installed the package into my local node_modules. As this package says in the README, it should be installed as a global package. I propose changing the isGlobal option passed to update-notifier to true, that way the command displayed in the update message will look like npm install -g npm-check-updates.

[raineorshine]

Great, thanks!