added DockerStartTask that allows starting an existing container
added DockerStartTask that allows starting an existing container, plus unit and integration tests
Merge branch 'master' of https://github.com/germanSancho/gradle-docker-plugin

Conflicts:
	src/main/groovy/de/gesellix/gradle/docker/tasks/DockerStartTask.groovy
Merge pull request #18 from germanSancho/master

add DockerStartTask that allows starting an existing container, plus unit and integration tests