get rid of preferGlobal in package.json

[andrewrk]

It's always better to install modules and version lock modules on a per-project basis. istanbul is no exception.

This project over here might have scripts to run tests and coverage that depend on istanbul version xyz, and this project over there might depend on istanbul version abc. This is what devDependencies are for. The point of package.json is so that you can run npm install and have all the dependencies and devDependencies installed. You don't want to also have to include instructions in the README that say, oh yeah, after you do npm install, you also have to manually install istanbul.

You can access istanbul via /node_modules/.bin/istanbul once you install it local to the project. Look how real world projects use istanbul. This is an example of a correctly organized project, and it has to deal with the preferGlobal warning.

There is no reason for preferGlobal, and in fact it gives new Node.js developers bad habits. Please remove it from your package.json.

[gotwarlost]

Agreed on your points. Easier to fix if this is a pull request :)