using as a forum / comments feed

re: https://github.com/TelescopeJS/Telescope/issues/559 

I created a quick spike to show embedding a header object in a post. I don't expect you'll merge this but it maybe useful to someone.
points: 

- allows you to embed a heading DIV if a post has a certain category checked ("topic" in this example)
- adds the heading using a separate package and `postHeading.push`
- uses the title field of the post to look for a matching topicData
- reads that heading using a meteor Method
- puts data into a reactiveVar. 
this is a bit hacky currently as it won't work with multiple instances of the template, so I've only enabled it for the "posts" view of one item.

also I found that by simply removing the URL field from the "new post" Telescope works well as just an internal forum app. Any posts then link automatically to the discussion.

so the idea would be that if you have a blog engine on the same site, and post a blog with a specific title, you would also create a Post on the fly, and then the post would automatically embed the blog content at the top of the post page, with comments etc as per normal telescope.

I didn't touch telescope itself much to do this, most of the code is in the new package.
I'm sure there are many ways to improve this, and comments on the PR would be great so I can maybe take a proper crack at a more useful integration.


![image](https://cloud.githubusercontent.com/assets/514002/5214123/d45236e8-75cc-11e4-9fee-edbdde526d8b.png)