CRAN release 0.2.2

Minor improvement

• update(, collapse_m = m) will now produce a level "other p" for the p least frequent categories #52.
• update() has received new default: collapse_m = 15 (was 30) #54.
• Missing values in y are now checked after removing observations without positive weights #56.
• Plotted lines now skip missing values on the y-axis, also in the ribbons #57.
• Factors with explicit NA level are respected, #59.
• Empty factor levels are being dropped, #60.

Maintenance

• Improved logic to find discrete grids for PDPs, #61.
• Better test coverage for fcut(), #63.