Use analysis-core as a base

[md5]

It seems like using the analysis-core plugin as a base for this one would be helpful. It would allow most of the code in this plugin to go away, could make it simpler to add things like simplecov support (cf. #11), and would provide richer trend graphing and other features.

That being said, I also feel like each of the metrics covered by this plugin should be split into their own plugins in that case, since there wouldn't be much common code if any left in this plugin.

[md5]

On second thought, it looks like analysis-core is really meant more for things that have a count as opposed to things like coverage that have percentages... I think it would fit with some of the metrics in this plugin, but perhaps not all of them.

[pkuczynski]

Another alternative would be to rewrite this plugin in Ruby, as it covers Ruby related metrics, it might get far more attention from the community:

https://wiki.jenkins-ci.org/display/JENKINS/Jenkins+plugin+development+in+Ruby

[md5]

I started to investigate that, but the mechanisms for doing so seem pretty bit-rotted. I think it would be worth the effort to bring those mechanisms back into alignment with a more modern Jenkins and JRuby version, but it requires a greater depth of Jenkins knowledge than I currently possess (not to mention that I don't personally have the time to dedicate to such an effort). Beyond that, I also think this plugin should be split up, as I mentioned in this issue.