Update CPUCollector docs

Author: Scott Cunningham

docs/collectors/CPUCollector.md

@@ -17,6 +17,7 @@ Setting | Default | Description | Type
 --------|---------|-------------|-----
 byte_unit | byte | Default numeric output(s) | str
 enabled | False | Enable collecting these metrics | bool
+extended | False | return aggregate CPU% metric and complex CPU metrics | str
 measure_collector_time | False | Collect the collector run time in ms | bool
 metrics_blacklist | None | Regex to match metrics to block. Mutually exclusive with metrics_whitelist | NoneType
 metrics_whitelist | None | Regex to match metrics to transmit. Mutually exclusive with metrics_blacklist | NoneType
@@ -33,4 +34,3 @@ servers.hostname.cpu.total.nice 0.0
 servers.hostname.cpu.total.system 0.2
 servers.hostname.cpu.total.user 0.4
 ```
-