Disable Seccomp when running old Linux kernel

for those of us running i.e. a 2.x kernel with 3.x headers, for some reason
Well, `3.13 < 3.5` == `'3.13.0-29-generic' < '3.5'` == `true`, which isn't what we want. If you don't mind another dependency, I would add [semver](https://github.com/isaacs/node-semver) so we can get `semver.lt('3.13.0-29-generic', '3.5.0')` == false