Follow Ruby standards for return boolean

Follow Ruby standards when returning a boolean value. This means using question marks in method names which return either true or false.

Author: kkirsche

elasticsearch-api/lib/elasticsearch/api/actions/indices/exists.rb

@@ -7,7 +7,7 @@ module Actions
         #
         # @example Check whether index named _myindex_ exists
         #
-        #     client.indices.exists index: 'myindex'
+        #     client.indices.exists? index: 'myindex'
         #
         # @option arguments [List] :index A comma-separated list of indices to check (*Required*)
         # @option arguments [Boolean] :allow_no_indices Whether to ignore if a wildcard indices expression resolves into
@@ -26,7 +26,7 @@ module Actions
         #
         # @see http://www.elasticsearch.org/guide/reference/api/admin-indices-indices-exists/
         #
-        def exists(arguments={})
+        def exists?(arguments={})
           raise ArgumentError, "Required argument 'index' missing" unless arguments[:index]
 
           valid_params = [