v1.4.0

• ps is now under the MIT license.

• Process functions now default to the calling R process. So e.g. you can
  write simply ps_connections() to list all network connections of the
  current process, instead of ps_connections(ps_handle()).

• New ps_get_nice() and ps_set_nice() functions to get and set the
  priority of a process (#89).

• New ps_system_memory() and ps_system_swap() functions, to
  return information about system memory and swap usage.

• New ps_disk_partitions() and ps_disk_usage() functions, they
  return information about file systems, similarly to the mount and
  df Unix commands.