bugfix uint64 => int64

bugfix to match https://github.com/docker/docker/blob/228c6a374bf5fa47b0e19751ddc9148052bb7bbc/runconfig/config.go
container: add test for negative swap
authors: add Andreas Jaekle
all: get rid of the utils package

It wasn't that useful.
testing: simplify code
misc: add the function to parse the repository from the tag

In a full image name, it will split the repository from the tag, for
example tsuru/python:2.7, will split in "tsuru/python" and "2.7".

Related to 2dc7f6c67ceb195e23161418f45a60cee62da495.
merge