Add support for emoji :+1:

Hi,

First of all, thank you for creating this, I really like your extension, it makes it so much easier to understand the status of pending pull requests.

Now, we use the emoji :+1: a lot, so I added a very basic support to detect these emojis in addition to the current LGTM and plain +1s. As text() will not find the emojis, because they are within img tags, I changed text() to html() in the search, not sure if that might have a negative impact, it works for me pretty well, though.

Thanks,
Zaki