Add new parameter to GBM interface: modules.model.params.minobsinnode
Add support for weights in GBM and hierarchical modules.

Because hierarchical method sample unequally the space, they affect
GBM's loss function computation.  To mitigate this effect, this patch
add supports for weighting the GBM model to compensate the unequal
hierarchical sampling.
Fix bug when using GBM interface with 1D model
Remove dependency to MBESS package.
Fix AMART sampling on 1D spaces. Follow up to 3b49cee.
Amart: Fix benign mistake in distance computation

When computing distance between candidate points, we were not removing
the reponse column. Nevertheless, this was not affecting the distance
computation since at this stage, the response column contains only zeros.
Therefore, the distance computation was correct.
Remove fields dependency.
Inline uniform_sampling.c in sampler/amart

 * Simplifies ASK configuration (no need to build shared C library)
 * Amart code is self contained
Bump ASK version to 1.0.1

* Commit ASK documentation to main repository.
Add --version to argument parser
Nicer usage message for compare-time-series
Add top level Makefile