README.md: add some minimal information for this project

Author: unleashed

README.md

@@ -1,6 +1,27 @@
 echo-api
 ========
 
-Stupid sinatra app that returns back info about the request 
+Sinatra app that returns back info about HTTP/1 requests.
 
 https://echo-api.3scale.net/ 
+
+## Container image
+
+A container image can be found at quay.io/3scale/echoapi:stable.
+
+## Running on Openshift/Istio
+
+You can find contributed templates for deploying `echo-api` on Openshift
+and Istio in the `contrib` directory.
+
+## Running with Jaeger support
+
+Just pass in the environment variables below to the program:
+
+- `OPENTRACING_TRACER` set to `jaeger`.
+- `JAEGER_SERVICE_NAME` can optionally be set, default is `echo-api`.
+- `JAEGER_AGENT_HOST` set to the hostname/address of the Jaeger's agent.
+- `JAEGER_AGENT_PORT` set to the port where the Jaeger's agent listens.
+
+The `JAGER_AGENT_HOST` and `JAEGER_AGENT_PORT` variables can be omitted for
+a default local agent listening at `127.0.0.1` and port `6831`.