v0.4.2

• Fix bugs in expect_column_values_to_[not]_be_null: computing unexpected value percentages and handling all-null (thanks @ccnobbli)
• Support mysql use of Decimal type (thanks @bouke-nederstigt)
• Add new expectation expect_column_values_to_not_match_regex_list.
  • Change behavior of expect_column_values_to_match_regex_list to use python re.findall in PandasDataset, relaxing matching of individuals expressions to allow matches anywhere in the string.
• Fix documentation errors and other small errors (thanks @roblim, @ccnobbli)