Add grunt task to print duplicate modules

build/tasks/output-module-counts.coffee

@@ -0,0 +1,22 @@
+path = require 'path'
+
+module.exports = (grunt) ->
+  grunt.registerTask 'output-module-counts', 'Log modules where more than one copy exists in node_modules', ->
+    nodeModulesDir = path.resolve(__dirname, '..', '..', 'node_modules')
+
+    modules = {}
+    grunt.file.recurse nodeModulesDir, (absolutePath, rootPath, relativePath, fileName) ->
+      return if fileName isnt 'package.json'
+
+      {name} = grunt.file.readJSON(absolutePath)
+      modules[name] ?= 0
+      modules[name]++
+
+    sortedNames = Object.keys(modules).sort (name1, name2) ->
+      diff = modules[name2] - modules[name1]
+      diff = name1.localeCompare(name2) if diff is 0
+      diff
+
+    sortedNames.forEach (name) ->
+      count = modules[name]
+      grunt.log.error "#{name}: #{count}" if count > 1