LinkedIn Support

Per issue #92, I've added linkedin support through RSS. Configuration is as follows:

``` json
{
	"service": "linkedin",
	"user": "12345678",
	"url": "http://www.linkedin.com/rss/nus?key=fakeRssKeyTbHl4cb2ooRUtpi3wK1LNu6dfWHjNAoWWmqMIBNN7urxIBgSoTtIUgBj"
}
```

* `user` is your user id as visible when you view your own profile. e.g. http://www.linkedin.com/profile/view?id=12345678&trk=nav_responsive_tab_profile will have a user id of *12345678*
* `url` is the url to your [Network Updates](http://www.linkedin.com/rssAdmin?display=) feed.

Please note this service is different in the way it handles YQL ajax. To enable caching server-side, it exposes a global function, named *jlsLinkedinCallback* + *userId*. It also sets a a caching interval of 5 minutes (as opposed to 1 by default) on the response.