recosystem 0.4

IMPORTANT NOTES

The API of this package has changed since version 0.4, due to the API change of LIBMF 2.01 and some other design improvement.

• The cost option in $train() and $tune() has been expanded to and replaced
  by costp_l1, costp_l2, costq_l1, and costq_l2, to allow for more
  flexibility of the model.
• A new loss parameter in $train() and $tune() to specify loss function.
• Data input and output are now managed in a unified way via functions
  data_file(), data_memory(), out_file(), out_memory(), and
  out_nothing(). See section Data Input and Output below.
• As a result, a number of arguments in functions $tune(), $train(),
  $output(), and $predict() now should be objects returned by these
  input/output functions.