Add instructions for strong params gotcha

Instructs user to explicitly permit the _delete parameter cocoon relies on for nested objec deletion
Catch typo of `_delete`. Should be `_destroy`
Merge pull request #156 from f3ndot/strong-params-reminder

Add instructions for Strong Parameters/Rails 4 gotcha when deleting nested objects
Small changes to the wording of strong parameters gotcha.

- strong parameters can also be used as a gem in rails3
- the `_destroy` flag is not specific to cocoon, but
  rather to nested model handling in rails in general.
Fix deprecation warnings in dummy app
Remove temporary objects from association after their creation
Merge pull request #166 from ncoders/master

Clean up temporary association objects
Adapt README: `:force_non_association_create` is rendered obsolete.

I hope. I will not remove it yet for backward 
compatibility reasons. 
Not sure if somebody actually needs an object to be
_not_ created on the association. Maybe for 
other ORM's?
Add `:form_name` parameter. Fixes #153.

This gives users the option to use a different
form parameter than the default `f`.

Usage:

    link_to_add_association 'add something', form, :people, :form_name => 'person_form'
Adapted history.
Remember destroyed state after validation errors. Fixes #136 and #160.

The `link_to_remove_association` correctly keeps the `_destroy`
flag, and gets a class `destroyed` which is used to automatically
hide the nested element.
Version bump to 1.2.1
Regenerate gemspec for version 1.2.1
Explain required elements

Took me a little debugging effort to discover the css/html wrapping requirements. Something like this would have helped me a tad.
Merge pull request #170 from quicksnap/patch-1

Explain required elements
remove unnecessary query on removing field
Add multiple items on one click

I've added the option of a `count` parameter in #link_to_add_association helper.
When this is a valid integer, every click on the Add button will create that number of items.

Most of the code is in the javascript of course.
I also cleaned the code a little (newcontent_braced, newcontent_underscord function and create_new_id functions)

In my use case, next to the Add button I added a select tag that changes the count settings.

Example:

Markup (Haml):
  .add-task-items
    = link_to_add_association 'Add', f, :association
    %select
      %option 1
      %option 3
      %option 5

Code (JS):
  $('.add-task-items').on('change', 'select', function({
    count = $(this).val();
    $(this).closest('.add-task-items').find('.add_fields').data('count', count);
  });
Merge pull request #171 from skv-headless/master

remove unnecessary query on removing field
Merge pull request #175 from yoavmatchulsky/add_multiple_items

Add multiple items on one click
Version bump to 1.2.2