RESUtils.initObservers watches the real #siteTable for changes (e.g. modules.neverEndingReddit.loadNewPage).

The "sponsored link" on /r/all and large subs is currently wrapped in a `#siteTable` element. RES's siteTable watcher is listening for changes on that, rather than the actual link listings.

This change adds a guard against the advert #siteTable.
Merge pull request #274 from andytuba/mutation-observer

RESUtils.initObservers watches the real #siteTable for changes