Delete README.md

sample-functions/DockerHubStats/README.md

-Building:
-
-```
-# docker service rm hubstats ; docker service create --network=functions --name=hubstats alexellis2/dockerhub-stats
-```
-
-Query the function through the gateway:
-
-```
-# curl -X POST -d "alexellis2" -v http://localhost:8080/function/hubstats
-```
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