Allow regex for allowModules

[gpoitch]

Ability to use a string or regex for allowModules. For example, say I have a directory I alias in typescript/webpack/whatever to @foo, I want to to allow everything in that directory:

settings: {
    node: {
      allowModules: [/^@foo\//', 'bar']
    }
}

This should help address some other issues such as #217, #233 in a generic way.