use html key as html_options in form helpers

Before
```erb
<%= form_for @user, html: { class: 'form-class' } do |f| %>
  ...
  <%= f.select :roles, [['Regular', 1], ['Admin', 2]], { include_blank: true }, multiple: true %>

  <%= f.select :sub_roles, [['Regular', 1], ['Admin', 2]], {}, multiple: true %>
  ...
```
After
```erb
<%= form_for @user, html: { class: 'form-class' } do |f| %>
  ...
  <%= f.select :roles, [['Regular', 1], ['Admin', 2]], include_blank: true, html: { multiple: true } %>

  <%= f.select :sub_roles, [['Regular', 1], ['Admin', 2]], html: { multiple: true } %>
  ...
```

I think it will make it more readable
Also make it similar to `form_for`