title: removeColumn does not remove column with foreign key when using migrate:undo with Sequelize CLI
body: <p>I am using sequelize CLI for my DB. I needed to add column with foreign key (1:n relation) to an existing table, which went well, column was added succesfully and worked as expected. 
  Problem starts, when I run <code>db:migrate:undo</code> which is calling <code>down</code> function from migration. I am using <code>removeColumn</code> there, but it just won't delete the column, just proceed without any errors.</p>
  
  <p>Example of migration: </p>
  
  <pre><code>export default  {
    up: (queryInterface, Sequelize) =&gt; {
      queryInterface.addColumn('table', 'someId', {
        type: Sequelize.INTEGER,
        references: {
          model: 'someModel',
          key: 'id'
        },
        onUpdate: 'cascade',
        onDelete: 'set null'
      })
    },
  
    down: (queryInterface, Sequelize) =&gt; {
      queryInterface.removeColumn('table', 'someId')
    }
  };
  </code></pre>
  
  <p>The migration itself works fine, just undo is not deleting either column or foreign key, but proceed without any errors. 
  Expected behaviour is, that <code>removeColumn</code> deletes specified column and  related foreign keys.</p>