Stop changing the `title` text when there is nothing to change.

This should fix feedbin/support#356. But please test it again before pulling into master.

Another possibility would be to build this check into the `updateTitle` function and change `updateReadCount` to use that function. This would keep all `<title>` manipulation DRY and to a minimum whenever it is used. The exact two lines would work.

(Sorry for the newline character at the end, GitHub’s online editor does that…)