npm modularized

Hiya,

I'm trying to switch appium over to including all dependencies as npm modules. Currently, selendroid is a git submodule which we build using a shell script.

In this PR I've forked selendroid and added a package.json file so that it can be published to npm. There's a `prepublish` script which compiles all targets using maven, so that appium can just require the module and get a path to a compiled selendroid.apk.

Do you want to manage/maintain or control this npm module? I'll just keep merging in changes for each version of selendroid, and publishing, but in case you want control over it I'm happy to hand it all over and such.
I don't think we want this, because this is only grabbing this one artifact out of the repo and publishing it, basically it's "selendroid-but-only-the-part-appium-wants"... plus this isn't a node project by any means.

I'd leave it to dominik if he cares about owning the node package "selendroid". But ideally your package should be named something like "selendroid-for-appium" rather than taking just the name selendroid.

So, in general I'm :-1: on including this PR