v0.4.0: support for pandas v1.0 nullable types

New features

• support boolean, string, and Int64 new dtypes added in pandas v1.0
• support pandas up to v1.0.1

Deprecated features

• the str column type is considered deprecated and will be removed in a future version. Use object or string (pandas v1.0+) instead.
• support for python 3.5 will be removed in a future version.
• support for OrderedDict will be removed in a future version. On python3.6+, use dict instead.