Fix grammar and typos in fluentd README.md (influxdata#5127)

plugins/inputs/fluentd/README.md

@@ -3,10 +3,10 @@
 The fluentd plugin gathers metrics from plugin endpoint provided by [in_monitor plugin](http://docs.fluentd.org/v0.12/articles/monitoring).
 This plugin understands data provided by /api/plugin.json resource (/api/config.json is not covered).
 
-You might need to adjust your fluentd configuration, in order to reduce series cardinality in case whene your fluentd restarts frequently. Every time when fluentd starts, `plugin_id` value is given a new random value.
+You might need to adjust your fluentd configuration, in order to reduce series cardinality in case your fluentd restarts frequently. Every time fluentd starts, `plugin_id` value is given a new random value.
 According to [fluentd documentation](http://docs.fluentd.org/v0.12/articles/config-file), you are able to add `@id`  parameter for each plugin to avoid this behaviour and define custom `plugin_id`.
 
-example configuratio with `@id` parameter for http plugin:
+example configuration with `@id` parameter for http plugin:
 ```
 <source>
   @type http
@@ -36,7 +36,7 @@ example configuratio with `@id` parameter for http plugin:
 
 ### Measurements & Fields:
 
-Fields may vary depends on type of the plugin
+Fields may vary depending on the plugin type
 
 - fluentd
     - retry_count            (float, unit)