README: Add information about the modbus plugin.

diff --git a/README b/README
index 3a56fbe..1dd09df 100644 (file)
--- a/README
+++ b/README
@@ -147,6 +147,10 @@ Features
       Memory utilization: Memory occupied by running processes, page cache,
       buffer cache and free.
 
+    - modbus
+      Reads values from Modbus/TCP enabled devices. Supports reading values
+      from multiple "slaves" so gateway devices can be used.
+
     - multimeter
       Information provided by serial multimeters, such as the `Metex
       M-4650CR'.
@@ -541,6 +545,10 @@ Prerequisites
     Used by the `memcachec' plugin to connect to a memcache daemon.
     <http://tangent.org/552/libmemcached.html>
 
+  * libmodbus (optional)
+    Used by the `modbus' plugin to communicate with Modbus/TCP devices.
+    <https://launchpad.net/libmodbus>
+
   * libmysqlclient (optional)
     Unsurprisingly used by the `mysql' plugin.
     <http://dev.mysql.com/>