Updated test to demonstrate incorrect resolution of ${project.version} values

[nickcodefresh]

Added dependency between level-one module and level-three module in order to demonstrate incorrect ${project.version} resolution (see #7)

In see this issue, run mvn install -Dexternal.version-qualifier=abc and then mvn dependency:tree -Dexternal.version-qualifier=abc from within maven-external-version-plugin/src/it/multi-module. You'll get the error:

[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1.345 s
[INFO] Finished at: 2017-02-15T09:00:30+00:00
[INFO] Final Memory: 15M/303M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal on project level-one: Could not resolve dependencies for project com.example:level-one:jar:1.0-abc-SNAPSHOT: Failure to find com.example:level-three:jar:1.0-SNAPSHOT in https://artifactory.nativ-systems.com/artifactory/repo was cached in the local repository, resolution will not be reattempted until the update interval of central has elapsed or updates are forced -> [Help 1]
[ERROR] 
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.

Maven is trying to resolve com.example:level-three:jar:1.0-SNAPSHOT, not com.example:level-three:jar:1.0-abc-SNAPSHOT