Add function to get save directory
Create Stat class
Require Stat class
Move get_directory method to Stat class
Implement invoke_count
Revert "Not depend on strscan"

This reverts commit d09c6c0ebdd8c1ef25de0b5db696180a82173bb7.
Implement key_count
Require rserve
Implement very basic stat method
Implement total key count
Sort key count
Show a day of the week
Change method name: key_count -> key_count_hash
Implement most_frequent_keys
Create Rclient class
Create rdo method (for syntactic suger)
Show most frequent key barplot
Create get_dir method for internal use
Create r_init function and load libs for sequential mining
Show space as <Space>