scoped npm packages break Duo support

[ndhoule]

NPM released scoped packages to the public registry on 4/20/2015. Because Duo's require resolution is slightly different than npm's, Duo can't use any package that depends on a scoped package.

For example, attempting to include ndhoule/values:

var values = require('ndhoule/values');

// do something

Duo is able to resolve values itself, but cannot resolve its dependency to @ndhoule/keys.

For now I'm just try/catching around scoped package dependencies, but I imagine as scoped package adoption picks up it's going to become a bigger problem for Duo.

Related issue: #456

[ndhoule]

Changed the title to be a little more reflective of the actual problem.