Add line numbers in the output for faster spotting

Currently the only way to see the line number is to look at the stack trace. It takes some time for human eye to spot the line number from the mess so it would be a great addition if nodeunit could display the line number directly.

An idea how to accomplish this: loop through the lines of the stack trace until you hit the file that was specified in the command line "nodeunit foo.js". When you hit that line, use regular expression such as `line.exec(/(\d):\d+$/)` to match it.