CRAN release 0.2.21

Major changes:

• New pairwise parameter added to dodgr_dists_categorical (#201)
• New function: dodgr_dists_nearest() (#203)
• Updated weight_streenet() function for wt_profile="bicycle" to return
  many more bicycle-relevant columns (#207).
• Fix major bug in categorical dists routines that gave wrong values (#201; thanks to @xiaofanliang)
• Fix bug in add_nodes_to_graph, #103
• Add 2 new parameters to add_nodes_to_graph, "dist_tol" and "intersections_only" (#103)

Minor changes:

• Fix bugs that issued warnings in weight_streetnet.sc if no "lanes" or "junction" columns present.