Version conflict - Rosjava core / message generation

[jubeira]

Maven complains when adding rosjava as a dependency in a POM file.
Apparently, rosjava_core:rosjava depends on a certain version of rosjava_bootstrap:message_generation, but some dependencies of rosjava depend on other versions and this causes a conflict (I only saw this when using Maven, not Gradle).
A complete list of the messages causing the conflict can be seen here.
One option to fix this issue is to re-release those messages with proper dependencies.

[jubeira]

This issue is pretty much a duplicated of #27.
With #36 it should be solved.