add changelog and config file entries

CHANGELOG.asciidoc

@@ -40,6 +40,7 @@ https://github.com/elastic/apm-server/compare/71df0d96445df35afe27f38bcf734a0828
 - Add Kibana sourcefilter for `sourcemap.sourcemap` {pull}454[454]
 - Increase default 'ConcurrentRequests' from 20 to 40{pull}492[492]
 - Add Config option for excluding stack trace frames from `grouping_key` calculation {pull}482[482]
+- Expose expvar {pull}509[509]
 
 ==== Deprecated
 

_meta/beat.reference.yml

@@ -69,3 +69,11 @@ apm-server:
       # If the default index pattern at 'outputs.elasticsearch.index' is changed,
       # a matching index pattern needs to be specified here.
       #index_pattern: "apm*"
+
+  # golang expvar support - https://golang.org/pkg/expvar/
+  #expvar:
+  # Set to true to Expose expvar
+  #enabled: false
+
+  # Url to expose expvar
+  #url: "/debug/vars"

apm-server.reference.yml

@@ -70,6 +70,14 @@ apm-server:
       # a matching index pattern needs to be specified here.
       #index_pattern: "apm*"
 
+  # golang expvar support - https://golang.org/pkg/expvar/
+  #expvar:
+  # Set to true to Expose expvar
+  #enabled: false
+
+  # Url to expose expvar
+  #url: "/debug/vars"
+
 #================================ General ======================================
 
 # The name of the shipper that publishes the network data. It can be used to group