xgb2sql 0.1.2

This is the first version on CRAN.
Avaible functions are onehot2sql() and booster2sql().

xgb2sql 0.2.0.9000

Fix issue for onehot2sql() processing data.frame with only one categorical feature.
Stop onehot2sql() and add stop message when there is no categorical feature in the input data.