Feature/allow dependency snapshots

[ascheman]

This is my solution to #38

[danielflower]

Good to hear you've found the plugin useful.

Just so I can fully understand this: is the use case where projects A and B are in different Git repos? If so, could you make the end to end test more complete by releasing the depended-on project multiple times and confirming the latest version gets picked up?

I've never seen things like the ArtifactFactory/MetaDatasource classes - are those just checking in the local repo for versions? Or the remote one too?

Also note that the Travis build has failed with the following message:

[ERROR] /home/travis/build/danielflower/multi-module-maven-release-plugin/src/main/java/com/github/danielflower/mavenplugins/release/PomUpdater.java:[167,21] cannot find symbol
  symbol:   method sort(<anonymous java.util.Comparator<org.apache.maven.artifact.versioning.ArtifactVersion>>)
  location: variable versions of type java.util.List<org.apache.maven.artifact.versioning.ArtifactVersion>

See https://travis-ci.org/danielflower/multi-module-maven-release-plugin/builds/160907059

[rverma-nikiai]

@danielflower Would love to see this PR get merged. We need support for snapshot repository upload.
Also the default upload logic need to get relaxed for the snapshot. Would be nice if we can run snapshot target without commit.

[ascheman]

@rverma-nikiai have you seen that @danielflower likes to get an extended end2end test to accept the contribution. I am not actively using the plugin any longer so I have no motivation to provide the extension currently. Feel free to take over the current state and help to complete it as required.

[ascheman]

I have rebased my changes to the latest 3.0-SNAPSHOT on origin/master (and created a 3.1-SNAPSHOT out of it as suggested by the CONTRIBUTING guide). Now it is up to you, @rverma-nikiai and @danielflower to finish and merge my work.