Pin packages to major releases

[beaugunderson]

While not all npm libraries abide by strict semver, ipv6 is one that does--meaning that when I change the major version number there are breaking changes. I have some re-organization planned for 4.0.0 so anon should be pinned to 3.x. When I release 4.0.0 I will also see if there are any changes needed in anon and send a pull request if so. :)

[edsu]

Thanks for the heads up.