ECS compliance - http.method

[cbeaujoin-stellar]

Currently it is http.method but according to ECS documentation (https://www.elastic.co/guide/en/ecs/1.0/ecs-http.html), it should be http.request.method

logstash-input-http/lib/logstash/inputs/http.rb

Line 251 in 879eb14

event.set("[http][method]", request_method) if request_method

#137