Allow keeping of temporary uuid tag

otherwise, if no user tags are provided, the call to delete the uuid tag
will delete the image itself.

this commit also adds usage to the example code and does not break
backwards compatibility
Adding some comments to make the linter happy
Exporting DATE in the makefile to unbreak goveralls task
TRIVIAL rename function [ci skip]
Giving a LogEntry an easy way to print
Updating deps
Merge pull request #20 from winchman/allow-keeping-of-temporary-uuid-tag

Allow keeping of temporary uuid tag