Version 0.7.0

We refined the internal structure, improved the documentation and added new functionalities in the past week.

We also added the following features:

koalas:

• read_clipboard (#430)
• read_excel (#430)
• read_html (#430)

koalas.DataFrame:

• at (#384)
• nunique (#346)
• add_prefix (#414)
• add_suffix (#414)
• add (#427)
• radd (#427)
• div (#427)
• divide (#427)
• rdiv (#427)
• truediv (#427)
• rtruediv (#427)
• mul (#427)
• multiply (#427)
• rmul (#427)
• sub (#427)
• substract (#427)
• rsub (#427)

koalas.Series:

• at (#384)
• nunique (#346)
• add_prefix (#414)
• add_suffix (#414)
• transform (#428)