renaming plugins -> inputs

plugins/inputs/influxdb/README.md

@@ -0,0 +1,72 @@
+# influxdb plugin
+
+The influxdb plugin collects InfluxDB-formatted data from JSON endpoints.
+
+With a configuration of:
+
+```toml
+[[inputs.influxdb]]
+  urls = [
+    "http://127.0.0.1:8086/debug/vars",
+    "http://192.168.2.1:8086/debug/vars"
+  ]
+```
+
+And if 127.0.0.1 responds with this JSON:
+
+```json
+{
+  "k1": {
+    "name": "fruit",
+    "tags": {
+      "kind": "apple"
+    },
+    "values": {
+      "inventory": 371,
+      "sold": 112
+    }
+  },
+  "k2": {
+    "name": "fruit",
+    "tags": {
+      "kind": "banana"
+    },
+    "values": {
+      "inventory": 1000,
+      "sold": 403
+    }
+  }
+}
+```
+
+And if 192.168.2.1 responds like so:
+
+```json
+{
+  "k3": {
+    "name": "transactions",
+    "tags": {},
+    "values": {
+      "total": 100,
+      "balance": 184.75
+    }
+  }
+}
+```
+
+Then the collected metrics will be:
+
+```
+influxdb_fruit,url='http://127.0.0.1:8086/debug/vars',kind='apple' inventory=371.0,sold=112.0
+influxdb_fruit,url='http://127.0.0.1:8086/debug/vars',kind='banana' inventory=1000.0,sold=403.0
+
+influxdb_transactions,url='http://192.168.2.1:8086/debug/vars' total=100.0,balance=184.75
+```
+
+There are two important details to note about the collected metrics:
+
+1. Even though the values in JSON are being displayed as integers, the metrics are reported as floats.
+JSON encoders usually don't print the fractional part for round floats.
+Because you cannot change the type of an existing field in InfluxDB, we assume all numbers are floats.
+
+2. The top-level keys' names (in the example above, `"k1"`, `"k2"`, and `"k3"`) are not considered when recording the metrics.