himach v0.3.0

• New graphics options:
  ** in map_routes colour lines by a flight frequency variable or by number of accelerations to supersonic;
  ** now can also plot a simple speed/distance/time/altitude profile with profile_routes.
• Added a section on cache housekeeping to the advanced vignette.
• Bug fixes: Solved map 'leakage' at dateline, and make_AP2 copes with vectors of airport pairs correctly now.

Now on CRAN.