Update batch size in record reader

[sadikovi]

This PR updates batch size from 256 to 1024. I also removed TODO for reader properties.

[sadikovi]

@sunchao could you review? Thanks!

[coveralls]

Pull Request Test Coverage Report for Build 622

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 11 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.008%) to 95.544%

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Files with Coverage Reduction	New Missed Lines	%
encodings/encoding.rs	1	94.77%
file/properties.rs	10	92.55%
<!--	Total:	11		-->

Totals
Change from base Build 619:	-0.008%
Covered Lines:	12414
Relevant Lines:	12993

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💛 - Coveralls