Update test schema.rb to match current migration

However, set force: true and didn't set indices

Fixes test failures for postgresql::

No integer type has byte size 11. Use a numeric with precision 0
instead.

https://travis-ci.org/mbleigh/acts-as-taggable-on/jobs/15196579

see rails/rails#6272

spec/schema.rb

@@ -1,59 +1,63 @@
 ActiveRecord::Schema.define :version => 0 do
-  create_table "taggings", :force => true do |t|
-    t.integer  "tag_id",        :limit => 11
-    t.integer  "taggable_id",   :limit => 11
-    t.string   "taggable_type"
-    t.string   "context"
-    t.datetime "created_at"
-    t.integer  "tagger_id",     :limit => 11
-    t.string   "tagger_type"
+  create_table :tags, :force => true do |t|
+    t.string :name
   end
 
-  add_index "taggings", ["tag_id"], :name => "index_taggings_on_tag_id"
-  add_index "taggings", ["taggable_id", "taggable_type", "context"], :name => "index_taggings_on_taggable_id_and_taggable_type_and_context"
+  create_table :taggings, :force => true do |t|
+    t.references :tag
 
-  create_table "tags", :force => true do |t|
-    t.string "name"
+    # You should make sure that the column created is
+    # long enough to store the required class names.
+    t.references :taggable, :polymorphic => true
+    t.references :tagger, :polymorphic => true
+
+    # Limit is created to prevent MySQL error on index
+    # length for MyISAM table type: http://bit.ly/vgW2Ql
+    t.string :context, :limit => 128
+
+    t.datetime :created_at
   end
-
+  # above copied from
+  # generators/acts_as_taggable_on/migration/migration_generator
+
   create_table :taggable_models, :force => true do |t|
     t.column :name, :string
     t.column :type, :string
   end
-  
+
   create_table :non_standard_id_taggable_models, :primary_key => "an_id", :force => true do |t|
     t.column :name, :string
     t.column :type, :string
   end
-  
+
   create_table :untaggable_models, :force => true do |t|
     t.column :taggable_model_id, :integer
     t.column :name, :string
   end
-  
+
   create_table :cached_models, :force => true do |t|
     t.column :name, :string
     t.column :type, :string
     t.column :cached_tag_list, :string
   end
-  
+
   create_table :other_cached_models, :force => true do |t|
     t.column :name, :string
     t.column :type, :string
-    t.column :cached_language_list, :string    
+    t.column :cached_language_list, :string
     t.column :cached_status_list, :string
     t.column :cached_glass_list, :string
   end
-  
+
   create_table :users, :force => true do |t|
     t.column :name, :string
   end
-  
+
   create_table :other_taggable_models, :force => true do |t|
     t.column :name, :string
     t.column :type, :string
   end
-  
+
   create_table :ordered_taggable_models, :force => true do |t|
     t.column :name, :string
     t.column :type, :string