Update jgit to prevent a critical Git security vulnerability

[szpak]

https://github.com/blog/1938-git-client-vulnerability-announced

Version 3.5.3.201412180710-r should be not affected.

[ajoberstar]

Thanks for sending that in. Unfortunately, I've had trouble upgrading JGit for a while now which is the only reason I'm still on 3.3.x. There seems to be a behavior change that exhibits in the LogCommand, causing the order to be off in some cases.

Given most use cases of Grgit are with Gradle, I would expect that the "untrusted" hosts portion doesn't apply as much. I just commented on an issue that may be related to my LogCommand problems, so I'll see if anything comes of that.