Move node-perseus.js to tools/
Move node-perseus.js to tools/

Summary: Move node-perseus.js out of the perseus-package, because it's
not going to be bundled in a package.

Test plan:
 - `make subperseus`

Auditors: aria

abe4mvp/perseus,ariabuckles/perseus,ariabuckles/perseus,daukantas/perseus,chirilo/perseus,iamchenxin/perseus,sachgits/perseus,learningequality/perseus,ariabuckles/perseus,sachgits/perseus,daukantas/perseus,alexristich/perseus,ariabuckles/perseus,abe4mvp/perseus,alexristich/perseus,chirilo/perseus,learningequality/perseus,iamchenxin/perseus