BUG: Bug in Series 0-division with a float and integer operand dtypes  (GH7785)
Merge pull request #7786 from jreback/div

BUG: Bug in Series 0-division with a float and integer operand dtypes  (GH7785)
TST: unicode compat for test_astype_unicode (GH7758)
dropna added for unique method. Performance improvements for nunique method.

ref pydata/pandas#7771

much faster.