Add media dimensions (#2448)

* Fixes #1985

- add migration AddMediaAttachmentMeta, which add meta field to media_attachments
- before saving attachment, set file meta if needed
- add meta in api

* add spec

* align the “size” format for image and video

* fix code climate

* fixes media_attachment_spec.rb

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20170424112722) do
+ActiveRecord::Schema.define(version: 20170425131920) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -120,6 +120,7 @@ ActiveRecord::Schema.define(version: 20170424112722) do
     t.datetime "updated_at",                     null: false
     t.string   "shortcode"
     t.integer  "type",              default: 0,  null: false
+    t.json     "file_meta"
     t.index ["shortcode"], name: "index_media_attachments_on_shortcode", unique: true, using: :btree
     t.index ["status_id"], name: "index_media_attachments_on_status_id", using: :btree
   end
@@ -332,4 +333,4 @@ ActiveRecord::Schema.define(version: 20170424112722) do
   end
 
   add_foreign_key "statuses", "statuses", column: "reblog_of_id", on_delete: :cascade
-end
+end