Update README.md (#1622)

* Update README.md

Clean up minor typos and syntax.

* Update README.md

Fix typo in 'default'

plugins/inputs/mesos/README.md

@@ -39,9 +39,9 @@ For more information, please check the [Mesos Observability Metrics](http://meso
   # slave_tasks = true
 ```
 
-By dafault this plugin is not configured to gather metrics from mesos. Since mesos cluster can be deployed in numerous ways it does not provide ane default
-values in that matter. User needs to specify master/slave nodes this plugin will gather metrics from. Additionally by enabling `slave_tasks` will allow
-agthering metrics from takss runing on specified slaves (this options is disabled by default).
+By default this plugin is not configured to gather metrics from mesos. Since a mesos cluster can be deployed in numerous ways it does not provide any default
+values. User needs to specify master/slave nodes this plugin will gather metrics from. Additionally, enabling `slave_tasks` will allow
+gathering metrics from tasks running on specified slaves (this option is disabled by default).
 
 ### Measurements & Fields: