Adopt automated code formatting

[jmccance]

Benefits of automated code formatting:

• We'll have a standard style, which helps make the codebase more readable for newbies and oldies alike
• Automation drastically reduces back-and-forth over style; we just go with what the formatter provides
• Reduces merge conflicts from intentional or accidental formatting changes
• Reduces noise in PRs from people fixing formatting errors when they find them (or having to submit separate formatting PRs)

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I propose we use ktlint.

• Implements a combination of the official Kotlin and Android style guides.
• Formatters available for major editors, including IntellIJ, Emacs, and Vim
• Minimally configurable, which helps keep us from bikeshedding over small style choices
• A number of options for Gradle integration. (I usually just re-use a simple buildSrc plugin I wrote.)

[jmccance]

I can add this very quickly, but would like to wait for #26 to be merged first.

[mihn]

👍🏼for automating this.