bring back the explaination of our LGTM process

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@fosiki.com> (github: SvenDowideit)
rewrite the PostgreSQL example using a Dockerfile, and add details to it

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@home.org.au> (github: SvenDowideit)
Merge pull request #4050 from SvenDowideit/put-back-LGTM

bring back the explanation of our LGTM process
Merge pull request #4034 from SvenDowideit/postgres-example

rewrite the PostgreSQL example using a Dockerfile, and add details to it
New package `nat`: utilities for manipulating the text description of network ports.

This facilitates the refactoring of commands.go

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)
fix underline/heading

Docker-DCO-1.1-Signed-off-by: Andy Rothfusz <github@developersupport.net> (github: metalivedev)
Merge pull request #4079 from shykes/separate-nat

New package `nat`: utilities for manipulating the text description of network ports
Make volumes-from populate if the volume is empty

This makes volumes-from behave just like a normal volume.