install instructions use unprefixed fedora image

Signed-off-by: Lokesh Mandvekar <lsm5@redhat.com>
Update instructions for mtu flag for Docker on GCE
Fixed error in group add example

There is no ${USERNAME} in bash, only ${USER}
Simplified and streamlined Amazon Quickstart

The amazon quickstart images are EBS backed and include cloudinit. I've personally tested these documentation changes as a new user to Docker.
Tweak formatting for GCE instructions
fix error on docker wait
Missing pipe in line 85
Fixed #3481 - Added Ubuntu Saucy to installation

Docker-DCO-1.0-Signed-off-by: James Turnbull <james@lovedthanlost.net> jamtur01
Only get rootfs when we need to calculate the image size

Docker-DCO-1.0-Signed-off-by: Michael Crosby <crosby.michael@gmail.com> (github: crosbymichael)
Fix Travis handling of a fully-numeric commit hash being YAML-converted to a number instead of a string

Docker-DCO-1.0-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Merge pull request #3491 from tianon/travis-numeric-commit

Fix Travis handling of a fully-numeric commit hash being YAML-converted ...
Merge pull request #3487 from crosbymichael/improve-images-speed

Only get rootfs when we need to calculate the image size
Merge pull request #3488 from jamtur01/1310

Fixed #3481 - Added Ubuntu Saucy to installation
Merge pull request #3461 from jbeda/patch-1

Update instructions for mtu flag for Docker on GCE
Merge pull request #3462 from tsaavik/patch-2

Simplified and streamlined Amazon Quickstart
Merge pull request #3483 from lukaspustina/patch-1

Missing redirect in line 85
Merge pull request #3430 from lsm5/fedora-official-image

install instructions use unprefixed fedora image
Fix ADD caching issue with . prefixed path

Docker-DCO-1.0-Signed-off-by: Guillaume J. Charmes <charmes.guillaume@gmail.com> (github: creack)
Make vfs error more explicit

Docker-DCO-1.0-Signed-off-by: Guillaume J. Charmes <guillaume.charmes@docker.com> (github: creack)
give more specific advice on setting up signing

Docker-DCO-1.0-Signed-off-by: Sven Dowideit <SvenDowideit@fosiki.com> (github: SvenDowideit)