Add Cortex & CrateDB as additioanl remote storage integrations.

Thanks to @juliusv for mentioning them in irc.

content/docs/operating/integrations.md

@@ -33,6 +33,8 @@ careful evaulation of any solution in this space to confirm it can handle your
 data volumes.
 
   * [Chronix](https://github.com/ChronixDB/chronix.ingester): write
+  * [Cortex](https://github.com/weaveworks/cortex): read and write
+  * [CrateDB](https://github.com/crate/crate_adapter): read and write
   * [Graphite](https://github.com/prometheus/prometheus/tree/master/documentation/examples/remote_storage/remote_storage_adapter): write
   * [InfluxDB](https://github.com/prometheus/prometheus/tree/master/documentation/examples/remote_storage/remote_storage_adapter): read and write
   * [OpenTSDB](https://github.com/prometheus/prometheus/tree/master/documentation/examples/remote_storage/remote_storage_adapter): write