Release agtboost 0.9.2

See NEWS.md for details
- Patch fixing slow gbt.save() functionality.
- Obtain XGBoost and LightGBM hyperparameters from gbt.complexity().
- Include attribute "offset" in gbt.train() and predict().
- Throw error when gb-loss-approximation deviates from true loss. Suggest lower learning_rate.
- Solves $\arg\min_\eta \sum_i l(y_i, g^{-1}(offset_i+\eta))$ numerically instead of simple average to obtain initial prediction
- Deprecate warnings for zero-inflation
- Decrease package size drastically by stripping debugging information

University of Alberta presentation

Update README with CRAN and agtboost paper

small cleanup