shapr 1.0.2

• Fix CRAN NOTE which turned out to be bug related to returning NULL rather than integer(0) to identify (unconditional)
  asymmetric causal sampling (#435)
• [Py] Get 'shaprpy' up to speed with the latest 'shapr' version and return the internal list properly
  (#436)
• Allow manual groups in explain_forecast() (#433)
• Minor updates to readme and pkgdown site after CRAN release of shapr 1.0.1
  (#437,
  #438)
• Require data.table >= 1.15.0 to allow uniform usage of by=.I
  (#434)
• Minor doc edits (#439)