"bullet-proof" maven (home) detection

Hey Kristian! I've previously run into issues but ignored them ... but I've run into another these days.

When testing JRuby-Rack I was getting a really strange "NPE from load-service" as I was loading a new runtime with the ENV cleared. 

https://github.com/kares/jar-dependencies/commit/93e5a557fc7e964cc99ca92d7939bb710c161a1b

Than there's a **<localRepository>** - I've a declaration in (global) *conf/settings.xml* so I made it work.

https://github.com/kares/jar-dependencies/commit/806895323424fc53175d1b3b598b664fa90f94c7

Also, I've performed some minor house keeping e.g. making the intended private methods private. 
I'm sorry about my editor removing (unnecessary) spaces from line ends, people previously complained that I was putting in junk spaces so that is how I roll ( can not make everyone happy :) ... if it's confusing just add `?w=1` when reviewing commits on GH.