*: add README

README.md

+# dex - A federated OpenID Connect provider
+
+dex is an OAuth2 server that presents clients with a low overhead framework for
+identifying users while leveraging existing identity services such as Google
+Accounts, FreeIPA, GitHub, etc, for actual authentication. dex sits between your
+applications and an identity service, providing a backend agnostic flavor of
+OAuth2 called [OpenID Connect](https://openid.net/connect/), a spec will allows
+dex to support:
+
+* Short-lived, signed tokens with predefined fields (such as email) issued on
+behalf of users.
+* Well known discovery of OAuth2 endpoints.
+* OAuth2 mechanisms such as refresh tokens and revocation for long term access.
+* Automatic signing key rotation.
+
+Any system which can query dex can cryptographically verify a users identity
+based on these tokens, allowing authentication events to be passed between
+backend services.
+
+One such application that consumes OpenID Connect tokens is the [Kubernetes](
+http://kubernetes.io/) API server, allowing dex to provide identity for any
+Kubernetes clusters.