Changed yamlKey regex to match valid keys like www.google.com

Hello

According to the [Yaml Reference Parser] [1] this document should be valid:

        www.google.com: yes
        www.yahoo.com: n

but vim syntax was failing to recognize '.' as valid. So I added it to the Regex that matches the yaml keys.

Thanks in advance


 [1]: http://yaml.org http://yaml.org/ypaste/