Learn about markdown tables extension.
Add initial support for pretty-printing GFM tables.

This solution is largely based on @gholt's blackfridaytext table
rendering code. It gave me motivation to work on this, and helped me
get a working version up and running very quickly. Thank you!
Add tests.
Add support for wide non-ascii characters.
Add support for table alignment.
Refactor to store table contents directly, avoid bytes.Split.
Merge pull request #5 from shurcooL/feature/tables

Add support for Markdown tables.