Add NODE_MODULE statement and change dash to underscore

This fixes the module for Node.js 0.9.x and above.
Merge branch 'master' of github.com:jamielinux/node-stringprep
0.1.6
0.1.5-test
0.1.5
0.1.6
Merge branch 'master' of github.com:astro/node-stringprep