Enhancements

@Wenq added contour.moments method.
@andreasgal added matrix.substract method.
@jainanshul added matrix.mean method.
@idubinskiy restored contour.points method.
@danschultzer updated node-pre-gyp to fix load of node-opencv in electron runtime.
@andreasgal made matrix.getData work with RGB images.
@Evilcat325 added matrix.MatchTemplateByMatrix method.
@danschultzer added code coverage.

Bug fixes

@dominikdolancic fixed image load issue in matrix.matchTemplate().
@AwooOOoo fixed type_info errors in Visual Studio with std namespace pollution.
@mvines fixed issue that prevented AsyncSaveWorker from using de-allocated memory.
@mcwhittemore fixed dissimilarity example image load.
@saoron fixed dead index.html documentup source.
@andreasgal fixed an issue with matrix.crop (and potentially others), where matrix.getData ends up returning less than full matrix.
@danschultzer fixed examples/test.js channel issue, and problematic Vec3b casting (instead of Vec3f) in matrix.set.

@dxprog changed readImage to load image with CV_LOAD_IMAGE_UNCHANGED instead of CV_LOAD_IMAGE_COLOR. The latter returned the image as 3-channel.
@danschultzer changed VideoCapture.close to VideoCapture.release.

Thanks to all, also a massive thanks to @danschultzer for helping get the open
tickets and PR's under control.