reset npm.cache hack in getNPM() breaks streams

[andrewdeandrade]

Streams2 has a lot of circular inheritance dependencies and instanceof checking.

Resetting the npm cache causes issues in https://github.com/iojs/readable-stream

Specifically, var Duplex = require('./_stream_duplex'); on https://github.com/iojs/readable-stream/blob/master/lib/_stream_writable.js#L139 causes the this instanceof Duplex check on https://github.com/iojs/readable-stream/blob/master/lib/_stream_writable.js#L143 to fail.

If there is truly no way to get around the npm.load issue, then @Raynos suggested that it may be best to change the implementation to run npm.load using child_process.spawn

Anyone have any better ideas?