Finally there's a better way to insert Emoji on a Mac.

Ryan McLeod has created Macmoji, which is essentially a list of terms and their corresponding Emojis. It lets you type Slack style tags like :cat: to insert 🐱.

The installation isn't hard at all, just check out the project on GitHub, download the .plist file, and then drag it onto the Text section of the Keyboard settings in System Preferences.