Reworking of the blacklist system. There is now one important key in rules to control blacklisting, called 'blacklist'
If set to true for a file, will blacklist npm modules named like that file.
Otherwise, it expects an array of things to blacklist, which can be core/npm modules or file-level modules,
qualified by the package they reside in.

Blacklisting is by tree -- that is if any of a required file's ancestors were blacklisted, it will be too.

e.g.
  blacklist: [
    'util', // blacklist core util
    'es5-ext', // blacklist whole npm module 'es5-ext'
    'readable-stream/transform', // blacklist transform.js in npm's readable-stream
    'redis/lib/util', // blacklist ./lib/util.js in the npm redis package
  ]