The docs/installation/mac guide causes a user to download the
`ubuntu` image, which defaults to `ubuntu:latest`.
After installing the next logical step is to work through
the userguide. If the userguide specifies ubuntu:14.04, then
a second ubuntu image will be downloaded.
On slow internet connections this takes a long time.
The cost of specificity in this case seems higher than the value.
Since this might be the first or second interaction a user has
with docker, they might not realize that they can remove the ":14.04"
bit to use the image that was previously downloaded.
Signed-off-by: Katrina Owen <katrina.owen@gmail.com>
68b07c0af9
