Unforeseeable errors with fetching the PSL url should no longer crash…

… tldextract, but simply be logged, while falling back to the bundled PSL.

Emergency hotfix to use GitHub mirror of the PSL

* Better CLI

* Cache env var support
* Python 3.3 support
* New aliases `suffix` and `registered_domain`
* Fix dns root label

fix john-kurkowski#22

bugfixes

almost 1.0 API

2 bug fixes

Forgot to include new resource .tld_set_snapshot. Load it via pkg_res…

…ources.