Value parser, for parsing a single value into a metric

closes #849

docs/DATA_FORMATS_INPUT.md

@@ -1,5 +1,12 @@
 # Telegraf Input Data Formats
 
+Telegraf is able to parse the following input data formats into metrics:
+
+1. InfluxDB Line Protocol
+1. JSON
+1. Graphite
+1. Value, ie 45 or "booyah"
+
 Telegraf metrics, like InfluxDB
 [points](https://docs.influxdata.com/influxdb/v0.10/write_protocols/line/),
 are a combination of four basic parts:
@@ -134,6 +141,38 @@ Your Telegraf metrics would get tagged with "my_tag_1"
 exec_mycollector,my_tag_1=foo a=5,b_c=6
 ```
 
+## Value:
+
+The "value" data format translates single values into Telegraf metrics. This
+is done by assigning a measurement name (which can be overridden using the
+`name_override` config option), and setting a single field ("value") as the
+parsed metric.
+
+#### Value Configuration:
+
+You can tell Telegraf what type of metric to collect by using the `data_type`
+configuration option.
+
+It is also recommended that you set `name_override` to a measurement name that
+makes sense for your metric, otherwise it will just be set to the name of the
+plugin.
+
+```toml
+[[inputs.exec]]
+  ## Commands array
+  commands = ["cat /proc/sys/kernel/random/entropy_avail"]
+
+  ## override the default metric name of "exec"
+  name_override = "entropy_available"
+
+  ## Data format to consume. This can be "json", "value", influx" or "graphite"
+  ## 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_INPUT.md
+  data_format = "value"
+  data_type = "integer"
+```
+
 ## Graphite:
 
 The Graphite data format translates graphite _dot_ buckets directly into