Allows transformed scripts to be parsed correctly
for dependencies. Currently, using these options
in combination with coffeeify or brfs (among
others) will throw a syntax error.

Right now, ids used to reference modules in external bundles are
required to correspond to actual files, but it'd be helpful if these ids
could be arbitrary. This issue has been brought up in browserify#387 and browserify#472.

A small change to how external modules are loaded, combined with using
the mdeps filter option, allows for arbitrary external ids. This commit
includes test coverage.

…on side effects in files with the same hash

…ependencies

…ecursive hash-aware dependency checker