Outdated readme.md

[victorwss]

The readme.md is too outdated. Firstly, it focuses primarily of FindBugs, which is quite much dead, leaving SpotBugs as an occasional second option.

Also, in the end, there are quite a lot of bad links:

Also, this part is laughably and misleading too old:

So, I think that the readme.md should be rewritten.

[JuditKnoll]

#479 partially fixes this issue, as it updates the links.
I set up the project with maven, and also I could not find bug-rank-check-style (the link does not work and a quick search was fruitless), so I could not update the ant setup.