sudo apt-get install -y libpurple-dev libjson-glib-dev libglib2.0-dev libprotobuf-c-dev protobuf-c-compiler mercurial make;
hg clone https://bitbucket.org/EionRobb/purple-hangouts/ && cd purple-hangouts;
make && sudo make install

Via EionRobb/purple-hangouts

And add proper emojis from unicode-emoji