Linking containers added to API example

Linking containers was not covered in the API documentation. I looked it up in the client source code and testing it manually.
Adds info on how to get env vars from container

Currently the docs just say "let's go into the container and look at the
env vars", but doesn't show how to do it.  It is also not currently
possible to enter the container as it is written in the doc
( container started with app.py and then somehow later on we have a
shell in the same container )

Docker-DCO-1.1-Signed-off-by: Brian Goff <cpuguy83@gmail.com> (github: cpuguy83)
Fix typo
Merge pull request #6411 from alazaro/patch-1

Fix typo
docs: add spotify docker-client link

Docker-DCO-1.1-Signed-off-by: Daniel Norberg <daniel.norberg@gmail.com> (github: danielnorberg)
Merge pull request #6416 from danielnorberg/dano/docs-spotify-client

docs: add spotify docker-client link
Note user name and password in docs on boot2docker

Docker-DCO-1.1-Signed-off-by: Nathan LeClaire <nathan.leclaire@docker.com> (github: nathanleclaire)
Merge pull request #6421 from nathanleclaire/doc_fix

Note user name and password in docs on boot2docker
Fixed whitespace errors
Merge pull request #6386 from cpuguy83/fix_link_docs

Adds info on how to get env vars from container
Fix missing leading slash for /bin/bash executable
Merge pull request #6429 from mika/patch-1

Fix missing leading slash for /bin/bash executable
Fix several typos

Docker-DCO-1.1-Signed-off-by: Michael Prokop <github@michael-prokop.at> (github: mika)
Merge pull request #6431 from mika/mika/typos

Fix several typos
Fix spelling and grammar errors; remove seemingly out-of-place words

Docker-DCO-1.1-Signed-off-by: AJ Bowen <aj@gandi.net> (github: soulshake)
docker-java has moved to new location
Merge pull request #6440 from marcuslinke/patch-1

docker-java has moved to new location
Merge pull request #6433 from soulshake/small-typos

Fix spelling and grammar errors; remove seemingly out-of-place words
Merge pull request #6378 from evanderkoogh/patch-1

Linking containers added to API example
Add support for IPv6 addresses in --dns parameters.

Docker-DCO-1.1-Signed-off-by: Jan Pazdziora <jpazdziora@redhat.com> (github: adelton)