Don't ship flow files

[realityking]

Looking a bit more at the structure of the npm package and where its size comes from (see #137), the flow files stood out.

There are currently no flow types and Flow does not interpret JSDoc comments. This reduces the size of the dist folder by ~60%.

[coveralls]

Pull Request Test Coverage Report for Build 252

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 72.948%

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Totals
Change from base Build 250:	0.0%
Covered Lines:	172
Relevant Lines:	236

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💛 - Coveralls

[realityking]

Made redundant by #147