Replace async-file with fs-extra to match other packages

[benbrown]

Fixes #786

Description

Replace async-file package with fs-extra.

These packages provide the same functionality with slightly different syntax.

Removing dependence on async-file reduces the packages we need to worry about.

Specific Changes

• replaced dependence in package file
• replaced calls to .delete with .remove
• replaced calls to .exists with .pathExists

Testing

Run existing tests

[coveralls]

Pull Request Test Coverage Report for Build #2040

• 5 of 5 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.02%) to 87.52%

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Totals
Change from base Build #2032:	0.02%
Covered Lines:	3006
Relevant Lines:	3306

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💛 - Coveralls

[stevengum]

LGTM!

@sgellock, should we start pinning dependencies as we add/change them and then pin the other libraries' dependencies as part of a work item?

[sgellock]

I'd propose we lock any sagger generated dependencies. Any of our 1st party components, e.g timex, etc. for 3rd party components, I'd propose we use ~ versioning and not ^ versioning.

[benbrown]

thank you gentlemen.