Add LICENSE to MANIFEST
Add LICENSE to MANIFEST

I'm building a version of `tldextract` using [`conda`](http://conda.pydata.org) for [conda-forge](http://conda-forge.github.io). When possible, we try to include a link to the license file in the `meta.yaml` specification. Doing so requires the LICENSE be linked in the manifest file.
john-kurkowski/tldextract,jvanasco/tldextract