Autosave

Adds autosave for previously created posts
Adds previews for posts
Adds JS alert when leaving a page with unsaved content
Hm, I think those are valid concerns, but would still like to keep the setTimeout out of saveForm. What about returning the deferred that $.ajax returns from saveForm, and then attaching the result handlers to it there? That would allow you to call saveForm independently, without inadvertently triggering a setTimeout.

```
  updateLater = (timer) ->
    timer = 120000  unless timer?
    timeoutId = window.setTimeout((->
      saveForm().done(->
        updateLater(10000)
      ).fail(->
        console.log "Something went wrong while trying to autosave..."
      )
    ), timer)
    return


  saveForm = () ->
    data = []
    data.push {name: "id", value: $("#main").data("post-id")}
    data.push {name: "post[draft_content]", value: $(".edit_post").last().find("#post_draft_content").val()}

    return $.ajax(
      type: "POST"
      url: "/dashboard/autosaves"
      data: data
    )
```