Add base for immutable Dockerfile
Add methods for all instructions
Move instructions to separate file
Change the toString method on Instruction to be the on the Dockerfile format
Change tests
Merge branch 'master' into immutable-dockerfile

Conflicts:
	src/main/scala/sbtdocker/Dockerfile.scala
	src/test/scala/sbtdocker/DockerBuilderSpec.scala
Add mutable Dockerfile
Add compatibility with version 0.3.0
Make mutable Dockerfile a case class
Cleanup
Stricter type parameter for DockerfileLike
Add examples with immutable Dockerfile
Add documentation for immutable and mutable Dockerfile
Change type of stageFiles
Rename class CopyPath to StageFile
Add stageFile tests for Dockerfiles
Set the version to 0.4.0-SNAPSHOT
Update Dockerfile text
Refactor example
Release version 0.4.0