CORE-1045: transitive dependencies in liquibase-maven-plugin

Hello! This is a fix for CORE-1045 bug.
The problem was that previously,  liquibase-maven-plugin resolved only the direct dependencies. 

Now, with this pull, liquibase-maven-plugin should be able to track down transitive dependencies.

I've tested it with the sample artifacts found on https://liquibase.jira.com/browse/CORE-1045
Let me know if you have some advices or anything else.