Allow loading emotes texture from remote URL

[codecat]

Currently, we can't load texture paths that are URL's: https://github.com/codecat/tm-better-chat/blob/52ddb00dab85c9691318ac0d23811051318c8faa/src/Emotes.as#L22-L23 We can make this work, but it does require fetching the texture asynchronously. This is a requirement for #8.