fix: Buffer is allow as body without encoding to string

[alexpts]

Added support for working with a Buffer as body of request

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[alexpts]

@googlebot I signed it!

[JustinBeckwith]

This is great - thanks!

[alexpts]

The release of a new version will help me a lot.
@JustinBeckwith can you release new npm version 7.1.0?

[JustinBeckwith]

Sure, we need to land some of the test coverage I added in #226 first though.