various command fixes

Indicating the repository and tag should be separated by a space and not a '/'. Also fixed a quote typo.
use su instead of sudo
Add several of the small make.sh fixes from #1920, and make the output more consistent and contributor-friendly, since release instructions already exist in release.sh
revert removal of slash betwixt user/repo
Merge pull request #1983 from blissdev/patch-1

various command fixes in postgres example
Merge pull request #1968 from tianon/hack-build-instructions

* Hack: Add several of the small make.sh fixes from #1920, and make the output more consistent and contributor-friendly