[Feature/Addition] Parsons table head

[elyse-weiss]

I would love for petl's head function to be built into Parsons. This allows you to just get the first X number of rows from a table. Sometimes you want to test code on a smaller subset of data, or something like that, and this is very helpful.

Detailed Description

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Possible Implementation

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[matthewkrausse]

@shaunagm Wanted to flag this as closed as we merged the new methods.

[shaunagm]

Thanks @matthewkrausse