Remove NSEC
Remove NSEC

It seems that since we've been building without NSEC, if you operate on a repository that had been cloned without NSEC, using NSEC to perform working directory diffs can be incredibly slow. To mitigate massive slow downs, we'll turn this off for now. It can still be enabled and recompiled on a fork of NodeGit fairly easily.

nodegit/nodegit,jmurzy/nodegit,nodegit/nodegit,jmurzy/nodegit,nodegit/nodegit,jmurzy/nodegit,nodegit/nodegit,jmurzy/nodegit,nodegit/nodegit,jmurzy/nodegit