Fix button_to helper for data-type option

[ihower]

We may use data-type attribute to set Ajax request type for "data-remote" requests. (see jquery-ujs wiki)
link_to helper has no problem, but button_to will add "data-type" to the wrong input tag and does not work:

 <%= button_to "foo", "/bar", :remote => true, "data-type" => "json" %>

 <form method="post" action="/bar" data-remote="true" class="button_to"><div><input data-type="json" type="submit" value="foo" />...</div></form>

The "data-type" should be in form tag with "data-remote" , not input tag. This patch result:

<form method="post" action="/bar" data-remote="true" data-type="json" class="button_to"><div><input  type="submit" value="foo" />...</div></form>

It will be nice also backport to 3-1-stable branch.

[spastorino]

+1 can you take a look at link_to also and the rest of the helpers to see if we can apply the same pattern?.
Thanks.

[spastorino]

Actually link_to uses tag_options so is right :)

[spastorino]

@ihower, we were discussing with @josevalim ... what about this way ...

<%= button_to "foo", "/bar", :remote => true, :form => { "data-type" => "json" } %>

Then is up to the user to pass whatever they want to build the form attributes.

[ihower]

That's great and more general. I send another pull request #3156