Online News on the Rise     News you choose. Watch your back, Tom. Look out, Dan and Peter. Your viewers are turning to the Internet. A poll this week shows more and more news junkies are clicking on for their news. According to the Pew Research Center, one in three Americans goes online for news these days. That compares to just one in five two years ago. And 15 percent say they go online for news at least once a week, up from 6 percent in 1998. Meantime, viewership for network news programs continues to shrink. You still watch us, though, right?