Removed tpope/vim-markdown

Add plasticboy/vim-markdown

Revert "Add plasticboy/vim-markdown"

This reverts commit 32995eeeea3a8eb82c35f5913a86b2a31a597047.

Revert "Revert "Add plasticboy/vim-markdown""

This reverts commit b9423a0a7dcb8143f4e708de5b3c6a5ababaf76e.

Revert "Markdown files now have 80 char textwrap."

This reverts commit 3ac74b0d908e7cfbdfd12f1ae569e75164775e8c.