Support directory requires

[guybedford]

Modules can import a directory by name, which results in the index being loaded from that directory. We should detect these require forms within the local package and convert them into the index reference.

[guybedford]

We can allow this in the following way:

When installing a package from npm, we check for any files called index.js in sub-directories. If such a file is found, we create a file with the same name as the directory, subdirectory.js, containing a direct link to the index file - module.exports = require('./subdirectory/index'). If such a file name already exists, we don't overwrite it. In this way we get a full match with npm behaviour!

[guybedford]

This is now supported.