Add test for issue #105

[robth]

Hi @bvarner, this PR offers a test for issue #105.

I've added a sample multi-module project in src/test/resources/multi-module-project-stub. It's just a parent POM with a single module. It is expected that:

• ${project.version} should also include the branch name (meaning that the version of the parent POM file should be correct), and
• the module POM file should have a parent/version including the branch name.

The test itself can be found in src/test/java/com/e_gineering/maven/gitflowhelper/DeployFeatureBranchIT.java.