v0.2.0

New features

• Added option to otp_get_isochrone() to return isochrone as either GeoJSON (default)
  or as a simple feature collection (sf). Specified using the new format argument (#4)

• Now also imports geojsonsf, used in otp_get_isochrone()

Bug fixes

• The unit of time returned by otp_get_times() was inconsistent. When the 'detail'
  parameter was set to TRUE the time was returned in seconds; otherwise the time was
  returned in minutes. This has been corrected so that time is always returned in
  minutes (#3).

• Remove 'curl' from 'Imports:' to fix CRAN binary build error on some platforms (#2)