code: public EtcdResponse put(final String key, final String value) throws EtcdException {
  		UriComponentsBuilder builder = UriComponentsBuilder.fromUriString(KEYSPACE);
  		builder.pathSegment(key);
  
  		MultiValueMap<String, String> payload = new LinkedMultiValueMap<>(1);
  		payload.set("value", value);
  
  		return execute(builder, HttpMethod.PUT, payload, EtcdResponse.class);
  	}
docs: Sets the value of the node with the given key in etcd. Any previously
  existing key-value pair is returned as prevNode in the etcd response.
  
  @param key
  the node's key
  @param value
  the node's value
  @return the response from etcd with the node
  @throws EtcdException
  in case etcd returned an error