Better meta attributes listing

source/scripts/controllers.js.coffee

@@ -41,6 +41,7 @@ angular.module("sideBySide.controllers", [])
 		headingKey = poems.config.heading or "Author"
 		$scope.headings = (version[headingKey] for version in transformed.meta)
 
+		$scope.metaKeys = poems.getMetaKeys()
 		$scope.all = poems.all
 		scroll()
 

source/scripts/services/poems.js.coffee

@@ -23,4 +23,9 @@ angular.module("sideBySide").service "poems", ->
 	@getInactive = ->
 		(poem for poem in @all when poem.meta.Active != true)
 
+	@getMetaKeys = ->
+		@all.reduce (all, one) ->
+			_.uniq all.concat (key for key of one.meta)
+		, []
+
 	@