Add a basic readme

README.rst

+Secure Access Token Authorizer
+==============================
+
+What is this?
+-------------
+
+Secure Access Token Authorizer is a `Tahoe-LAFS`_ storage-system plugin which authorizes storage operations based on privacy-respecting tokens.
+
+Such tokens derive from `PrivacyPass`_.
+They allow a Tahoe-LAFS client to prove it has a right to access without revealing additional information.
+
+Copyright
+---------
+
+   Copyright 2019 PrivateStorage.io, LLC
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+
+.. _Tahoe-LAFS: https://tahoe-lafs.org/
+
+.. _PrivacyPass: https://privacypass.github.io/