Fix the image markup on 'heygirl' command

[joepurdy]

Need to change the markup on the heygirl command so it doesn't include the image URL

Change:

heygirl: function() {
        return "http://40.media.tumblr.com/tumblr_lx7125u4h01r8lg7to1_500.png"
},

To:

heygirl: function() {
        return "[!heygirl](http://40.media.tumblr.com/tumblr_lx7125u4h01r8lg7to1_500.png)"
},

Should also add variety while we're at it with an array of pics.

[joepurdy]

These changes are live in production purdybot. Closing this out, thx @iheartkode