0.9999

• New module dataiter.regex for vectorized regular expressions
• Add proxy object Vector.dt for dataiter.dt
• Add proxy object Vector.re for dataiter.regex
• Add proxy object Vector.str for numpy.strings
• Use PyArrow instead of Pandas to read and write CSV files
• Replace Pandas dependency with PyArrow

This is likely to be a breaking change in some rare weirdly formatted
CSV files that Pandas and PyArrow might parse differently, resulting in
something like diffently guessed data types or differently detected
missing value markers. The note about stability below release 0.99 still
applies.