CRAN v0.0.9

Major changes:

• New function osmdata_sc to return data in silicate::SC format (see github.com/hypertidy/silicate; this also requires additional dependency on tibble)
• Structure of osmdata object modified to replace former $timestamp field with $meta field containing a list of $timestamp, $OSM_version (currently 0.6), and $overpass_version.
• add_osm_feature() now accepts vectors of multiple values (see #139).
• osmdata_sf() objects default to character vectors, not factors (see #44).

Minor changes:

• vignette updated
• Overpass URL now randomly selected from the four primary servers (see https://wiki.openstreetmap.org/wiki/Overpass_API#Public_Overpass_API_instances), thanks to @JimShady.
• bug fix for osmdata_sp() (see #56)
• osmdata_sp() fixed to return osm_id values (see #131; thanks @JimShady).