Revert "Set up `node-stringprep-icu` as optional dependency, update tests"

This reverts commit 96d2f0954ac068ddd086264c370ac1f9ef2ecc42.

Conflicts:
	package.json
add weird binding.gyp which checks for icu-config

only when icu-config is available it actually tries to build
node-stringprep.cc.

i added support for windows and linux seperatly like pg (node-postgres)
does. might not be pretty but looks like that it works (at least on my
machine it builds with and without libicu-dev without errors).
Haven't tested it on windows though.
broke dependencies during merge
build on freebsd
Merge pull request #48 from node-xmpp/errorfree-build

Errorfree build