upgrade(rails 5): no longer use rake to invoke rake tasks, use rails

though I left the case alone where the command would previously been
just `bundle exec rake`, as doing the same doesn't work for rails.

db/schema.rb

@@ -1,4 +1,3 @@
-# encoding: UTF-8
 # This file is auto-generated from the current state of the database. Instead
 # of editing this file, please use the migrations feature of Active Record to
 # incrementally modify your database, and then regenerate this schema definition.

db/seeds.rb

@@ -1,5 +1,5 @@
 # This file should contain all the record creation needed to seed the database with its default values.
-# The data can then be loaded with the rake db:seed (or created alongside the db with db:setup).
+# The data can then be loaded with the rails db:seed (or created alongside the db with db:setup).
 #
 
 users = [