0.4.0 (#39)

• Adopt pipda v0.4.2

Performance improved:

• Refactor core.grouped to adopt pandas's groupby
• Try to use DataFrame.agg()/DataFrameGroupBy.agg() when function applied on a single columns (Related issues: #27, #33, #37)

Fixed:

• Fix when data or context as new column name for mutate()
• Fix SettingwithCopyWarning in pivot_longer
• Use regular calling internally to make sure it works in some cases that node cannot be detected (ie Gooey/%%timeit in jupyter)

Added:

• datar.datar_versions() to show versions of related packages for bug reporting.