Add HTTP output plugin (#2491)

plugins/outputs/http/README.md

@@ -0,0 +1,28 @@
+# HTTP Output Plugin
+
+This plugin writes to a HTTP Server using the `POST Method`.
+
+Data collected from telegraf is sent in the Request Body.
+
+### Configuration:
+
+```toml
+# Send telegraf metrics to HTTP Server(s)
+[[outputs.http]]
+  ## It requires a url name.
+  ## Will be transmitted telegraf metrics to the HTTP Server using the below URL.
+  ## Note that not support the HTTPS.
+  url = "http://127.0.0.1:8080/metric"
+  ## Configure dial timeout in seconds. Default : 3
+  timeout = 3
+  ## http_headers option can add a custom header to the request.
+  ## Content-Type is required http header in http plugin.
+  ## so content-type of HTTP specification (plain/text, application/json, etc...) must be filled out.
+  [outputs.http.headers]
+    Content-Type = "plain/text"
+  ## Data format to output.
+  ## Each data format has it's own unique set of configuration options, read
+  ## more about them here:
+  ## https://github.com/influxdata/telegraf/blob/master/docs/DATA_FORMATS_OUTPUT.md
+  data_format = "influx"
+```