Add optional configurable quirks

[gfcittolin]

Sorry for not discussing it beforehand, but I had to do some changes to be able to parse some .dbf files I had here, and I thought it could be interesting to contribute the changes back to you.

I've chosen to add a quirks object in the options, so we can selectively enable these quirks (and maybe add others in the future), as I encountered them on the wild. This way, it's fully backwards-compatible with the current version. Unit-tests for them were also written.

Here they are if you find them interesting, but feel free to just ignore them otherwise :)

[coveralls]

Pull Request Test Coverage Report for Build 226

• 21 of 22 (95.45%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.7%) to 98.851%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
index.js	21	22	95.45%

Totals
Change from base Build 219:	-0.7%
Covered Lines:	150
Relevant Lines:	151

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💛 - Coveralls