don't mix understream in to underscore

If you mix understream in to underscore, it can really mess up versioning.

If package A requres version A of understream that is different than one of package A's dependencies (package B), then npm will install separate instances of understream for each package.

However, if package A and package B use the same version of underscore, there will only be one instance of underscore that they're mixing different instances of understream into, and whichever instance is mixed in last will be the instance that both packages are using.