Format long Float and Double fields

[sadikovi]

This PR addresses the issue in record reader of displaying long values of Field::Float and Field::Double. When value is long (value > 1e19 || value < 1e-15), we display it in scientific notation, otherwise the default one.

I found this definition of "long" values here: https://github.com/maciejhirsz/json-rust/pull/32/files#diff-d0b3721173a6539188b808c57c0b4b08R54

[sadikovi]

@sunchao Could you review this PR? Thanks!

[coveralls]

Pull Request Test Coverage Report for Build 598

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 9 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.009%) to 95.49%

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Files with Coverage Reduction	New Missed Lines	%
record/api.rs	9	96.96%
<!--	Total:	9		-->

Totals
Change from base Build 596:	0.009%
Covered Lines:	12048
Relevant Lines:	12617

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💛 - Coveralls