[plugins] include the readme warning in the plugins directory of the build

Gemfile.lock

@@ -19,6 +19,8 @@ GEM
     multipart-post (2.0.0)
     puma (2.9.0)
       rack (>= 1.1, < 2.0)
+    puma (2.9.0-java)
+      rack (>= 1.1, < 2.0)
     rack (1.5.2)
     rack-protection (1.5.3)
       rack
@@ -47,6 +49,7 @@ GEM
       rubyzip (>= 0.9, < 1.2)
 
 PLATFORMS
+  java
   ruby
 
 DEPENDENCIES

src/kibana/plugins/README.md

@@ -1,7 +0,0 @@
-# Kibana Plugins
-
-### Please don't write custom plugins
-
-While Kibana has a directory called plugins, and a way to load plugin-provided modules, the API is perpousfully undocumented as the underlying mechanisms making plugins possible are undocumented and very likely to change.
-
-Also, please keep in mind that, at this time, issues filed to aid in the development of plugins will be closed with a link to this file.

src/kibana/plugins/README.txt

@@ -0,0 +1,8 @@
+Kibana Plugins
+==================
+
+PLEASE DON'T WRITE CUSTOM PLUGINS
+
+While Kibana has a directory called plugins, and a way to load plugin-provided modules, the API and underlying mechanisms are purposefully undocumented, and are very likely to change.
+
+Issues filed to aid in the development of plugins will be closed with a link to this file.

tasks/build.js

@@ -20,6 +20,7 @@ module.exports = function (grunt) {
     'compile_dist_readme',
     'chmod_kibana',
     'make_plugin_dir',
+    'copy:plugin_readme',
     'describe_bundled_plugins',
     'copy:versioned_dist',
     'create_packages'

tasks/config/copy.js

@@ -72,6 +72,15 @@ module.exports = function (grunt) {
           dest: '<%= build %>/dist/kibana-' + version
         }
       ]
+    },
+
+    plugin_readme: {
+      files: [
+        {
+          src: '<%= build %>/kibana/public/plugins/README.txt',
+          dest: '<%= build %>/dist/kibana/plugins/README.txt'
+        }
+      ]
     }
 
   };