Intital pass at a printf implementation

[CaseyB]

This PR is a first pass at implementing printf to resolve #41

HappyHacktoberfest !

[CaseyB]

Sorry about that, the author info got screwed up so I had to update the commits.

[CaseyB]

Is there anything I'm missing? I believe this covers the core printf functionality.

[GrayJack]

Awesome! Thanks for the contribution 🎉

bors r+

[bors[bot]]

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