Changes in version 0.3.0 (2018-12-01)                  

  - made parameter 'log' able to take value from a 'log_arg' variable in
    the parent environment (dynamic scoping) of a function
      - the old way of assigning value to 'log' is still supported
  - new function:
      - wh_dict:	Create Data Dictionary from Data Warehouse
  - moved some codes to internal functions and internal variables
  - revised documentation
  - bug fixing

                 Changes in version 0.2.0 (2018-09-14)                  

  - new functions:
    1.  partition_random: partitioning a dataset randomly
    2.  encode_onehot: One Hot encoding
    3.  inspect_smap: a simplified thus faster version of inspect_map
  - rewrote codes that produce log files as internal functions
  - added vignettes
  - revised documentation
  - bug fixing