title: Plotting curved line in Python Basemap
body: <p>I would like to plot curved/arced lines on a Basemap map.
  I can plot a straight line using map.plot(x,y,..), but how do I make it curved/have arrows?</p>
  
  <p>In matplotlib, this can be done using annotate(..), but Basemap doesn't have this method.</p>
  
  <p>Any ideas?</p>