0.4.3 (#46)

• Adopt pipda 0.4.5
• Make dataset names case-insensitive;
• Add datasets: ToothGrowth, economics, economics_long, faithful, faithfuld, luv_colours, midwest, mpg, msleep, presidential, seals, and txhousing
• Add base.complete_cases()
• Change datasets.all_datasets() to datasets.list_datasets()
• Make sure assume_all_piping mode works internally: close #45