Bring node-osrm bindings into main project

[danpat]

At Mapbox, we primarily use OSRM via the node-osrm bindings. These currently live in a separate project, but are tagged and released in lockstep with osrm-backend.

This PR brings the node-osrm codebase into osrm-backend, and builds it at the same time as the rest of the code. This should reduce the friction we experience internally when needing to make osrm-backend features quickly available for NodeJS-based projects for folks not familiar with building C++ projects.

The only extra tools required are CMake 3.1, and npm install node-cmake.

TODO:

• make it compile and link against the current build (DONE: cmake -DNODEJS=ON .., off by default)
• import test suite and make it work (DONE: npm run node-test)
• enable static linking of dependencies for hassle-free npm install support on various platforms
• support easy publishing of binaries/build-from-source support (via Support for alternative build tools (node-cmake) mapbox/node-pre-gyp#205)
• CMake 3.1 will be required - update Travis build and dependency documentation.

@TheMarex please don't hate me.

[daniel-j-h]

Even Ubuntu 14.04 (LTS) does not ship with CMake 3.1+, so it's pretty bad wrt. building only osrm-backend or libosrm on different distributions. Could we at least decouple the root CMakeLists.txt from the Node.js binding's one only having the latter require CMake 3.1?

[danpat]

@daniel-j-h yeah, that's not a bad idea. Our node-osrm Travis build already pulls down cmake 3.2.x, so I'm OK requiring folks to get a newer cmake to get Node stuff.

[TheMarex]

Closing in favor of tracking in an issue since the code here is stale anyway. #3183