ie8 parses test results incorrectly

[JamesKyburz]

https://github.com/substack/tap-parser/blob/master/index.js#L63

fails because skip is never undefined but an empty string....

sane browser:/^(\d+)..(\d+)\b(?:\s+#\s+SKIP\s+(.*)$)?/.exec('1..2') // => ["1..2", "1", "2", undefined]

mad browser: /^(\d+)..(\d+)\b(?:\s+#\s+SKIP\s+(.*)$)?/.exec('1..2') // => ["1..2", "1", "2", ""]

[JamesKyburz]

#4 closes this.

Thanks @substack !