Support multiline strings

[blakeembrey]

Currently multiline strings aren't being rendered correctly within the table. I would expect it to automatically adjust to the longest line and not use all characters from the string in the length.

[blakeembrey]

Just realised that markdown doesn't support this, maybe replace with <br>?

[malgorithms]

I'd want to cover all possible cases with this...If you want to add optional features to tablify to (1) convert \n to br, and (2) pretty handle multiline cells, I would likely accept a pull request. both should be options, though.

I'm unlikely to get to this change myself soon.