Environment.md: reset_ps1 function now with whoami

After loading the pyenv, my ps1 loses all user info
instead of:
[masnes@localhost ~]$
I have:
(py3) ~$
This improves things a little by changing it to:
masnes ~$

Adding hostname may also be desireable, but I found that hostname
is too long (localhost.localdomain) in the vm. Hostname -s would
fix this, but I don't trust it.
Environment: add postgresql-devel to install list

Some of the pip scripts gave me an error before installing
postgresql-devel. So I'm adding it to the yum install list
Revert "Env: reset_ps1 function now with whoami"

This reverts commit a76f4bf98fb2d95976e614f95acbb2c351008788.

whoami is not needed if the user will always be vagrant
Merge remote-tracking branch 'upstream/master'
Merge pull request #4 from masnes/master

Add postgresql-devel to yum install list