Allow carriage returns

I use `textwidth` in my .vimrc file to impose hard carriage returns at 79 characters. However when entering Goyo with `:Goyo 79` this is lost and I get line wrapping instead. When exiting Goyo the wrapped line appears as a very long line. This doesn't make any sense to me.

Start by reproducing the behavior from a .vimrc with textwidth set to 79, then run :Goyo 79 and exit Goyo. Verify how hard carriage returns and wrapping change across those transitions; done means the configured hard breaks are preserved instead of becoming one long line.

Written by the indexing model from the issue text.