bugfix regex infinite loop and resource eating

I have to change this regex because it causes ruby process to reach 100% of cpu.
Please, check if its ok.
It only force a whitespace after <a, href could be in any order.
Check it with: 
```
"<a id='bad-regex' href=\"http://github.com\">Github</a>" =~ /<a\s.*href=\"(mailto:)?([^\"]*)\"[^>]*>((.|\s)*?)<\/a>/i
```