280 remove file io

[ethanbsmith]

removed disk i/o from critical path of functions that fetch data form the internet. these functions now operate entirely in memory

main drivers for this:

1. the original process created significant contention with other disk i/o operations. this was particularly apparent on large batch downloads with older, slower disks and database servers
2. the implementation pattern was inconsistent. some functions used an entirely in-memory path, while others used disk i/o with temporary files. all functions now consistently use the in-memory pattern

Fixes #280

[joshuaulrich]

Hi @ethanbsmith, thanks for working on this PR! Is it ready for review?

[ethanbsmith]

Yes.

…

________________________________ From: Joshua Ulrich <notifications@github.com> Sent: Saturday, October 26, 2019 5:52:25 AM To: joshuaulrich/quantmod <quantmod@noreply.github.com> Cc: Ethan Smith <ethan.smith@pobox.com>; Mention <mention@noreply.github.com> Subject: Re: [joshuaulrich/quantmod] 280 remove file io (#281) Hi @ethanbsmith<https://github.com/ethanbsmith>, thanks for working on this PR! Is it ready for review? — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub<#281?email_source=notifications&email_token=AF2ACB62STXTPOXA2324C4LQQQVPTA5CNFSM4JB6QN22YY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOECKGILA#issuecomment-546595884>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/AF2ACB7A6KVJGEBELPEZU4DQQQVPTANCNFSM4JB6QN2Q>.