Subversion migration cheat sheet (first-draft)

Cheat sheet for guidance on migrating and interoperation of Git, GitHub, and SVN.

[RENDERED](https://github.com/github/training-kit/blob/cheatsheet-subversion-migration/downloads/subversion-migration.md)
>  items have an explained behavior, others dont

Indeed. Haven't crafted those all, yet. Direct branch commits are welcome if you have descriptions for these sections that might've been successfully used "in the field" to parallel Git and SVN. :smile: