v0.2.0

Major update with (almost) all plotting routines shifted from graphics::plot
to ggplot2. All previous parameters specifying graphics devices (such as
heights and widths) no longer apply.

Changes:

• vignette downloading-data removed (incorporate in making-maps)
• vignette making-maps extended
• vignette making-maps-with-data added
• Extensive examples added to most functions
• click_map removed
• connect_highways renamed get_highway_cycle
• highways2polygon renamed connect_highways
• extract_highway, extract_highways, order_lines no longer exported
• extract_osm_objects now just returns objects (instead of $obj and
  $warn), and dumps warnings direct to screen.
• add_osm_groups now accepts lists of simple spatial points as groups
• Coordinate reference system properly attributed to all objects
• many tests added
• Change to ggplot2 has considerably changed structure of many functions. For
  details see function examples and vignettes