collaborators

Hey Elad

I'm working on adding collaborators to Blocipedia.

I'm getting an error "undefined method `title' for nil:NilClass" on the below block of code in collaborators/index.html.haml .  I'm a little confused because title is an attribute of a wiki and I pull the title on the wikis index page without any trouble.
```          
  %h1
    = @wiki.title
    collaborators
```

I'd also like you to double check my partial for adding collaborators. 
```
= form_for [@wiki, @collaborator], remote: true do |f|
  = f.label :name
  = f.text_field :name, class: 'form-control'
 
  =f.label :email
  =f.text_field :email,class: 'form-control'
  %br
  =f.submit "Add collaborator to wiki", class: 'btn btn-success'
```
The error is "undefined method `collaborators_path'".  I understand this because collaborators are nested under wikis, but I'm not sure how to reference the form to the wiki and the collaborator being added.

Any let you can shed?

Thanks!