Nested-Pandas v0.4.9

What's Changed

• adding explode by @Graciaaa3 in #327
• Enable boolean masking through nest accessor by @dougbrn in #329
• update nested describe docstring for error raise by @Graciaaa3 in #330
• Revisit nf.explode() for multiple columns and duplicated index by @hombit in #332
• fix nest_lists for non-unique index by @dougbrn in #337

Full Changelog: v0.4.8...v0.4.9