Pluralize -en to -ens instead of -ina (#174)

Plural rules with adding -s instead of changing ending to -ina are
considered to be correct (i.e. stamens instead of stamina) and do not
create false plural forms of common English words, such as "kitten".
They are still correctly singularized, though.

See: https://github.com/hanami/utils/issues/173

lib/hanami/utils/inflector.rb

@@ -91,10 +91,6 @@ module Hanami
       # @api private
       IFE  = 'ife'.freeze
 
-      # @since 0.4.1
-      # @api private
-      INA  = 'ina'.freeze
-
       # @since 0.4.1
       # @api private
       IS   = 'is'.freeze
@@ -373,8 +369,6 @@ module Hanami
           $1 + A
         when /\A(buffal|domin|ech|embarg|her|mosquit|potat|tomat)#{ O }\z/i
           $1 + OES
-        when /\A(.*)(en|#{ INA })\z/
-          $1 + INA
         when /\A(.*)(?:([^f]))f[e]*\z/
           $1 + $2 + VES
         when /\A(.*)us\z/

test/fixtures.rb

@@ -354,10 +354,6 @@ TEST_PLURALS = {
   'tomato'   => 'tomatoes',
   'torpedo'  => 'torpedos',
   'veto'     => 'vetos',
-  # en => ina
-  'stamen'  => 'stamina',
-  'foramen' => 'foramina',
-  'lumen'   => 'lumina',
   # a => ata
   'anathema'  => 'anathemata',
   'enema'     => 'enemata',
@@ -543,7 +539,9 @@ TEST_PLURALS = {
   'car'          => 'cars',
   'hive'         => 'hives',
   # https://github.com/hanami/utils/issues/106
-  'album'        => 'albums'
+  'album'        => 'albums',
+  # https://github.com/hanami/utils/issues/173
+  'kitten'       => 'kittens'
 }.freeze
 
 TEST_SINGULARS = {
@@ -572,6 +570,10 @@ TEST_SINGULARS = {
   # f => s
   'chief' => 'chiefs',
   'spoof' => 'spoofs',
+  # en => ina
+  'stamen'  => 'stamina',
+  'foramen' => 'foramina',
+  'lumen'   => 'lumina',
   # s => es
   'acropolis'  => 'acropolises',
   'chaos'      => 'chaoses',