Markdown formatting; Vim plugins; Documentation

* Add mdpretty command to (re-)format a markdown file with Pandoc
* Add tpope's unimpaired vim plugin
* Improve Makefile output to be cleaner and easier to copy and paste
Documentation; Commands

* Explain a bit more in the README; re-wrap it
* Rename mdprettynowrap to nmdpretty
* The mdpretty commands cat the file afterwards
* Add 'watch' to list of recommended brew installs