Find the image ID of the container you wish to push with the command docker images. Then, you can tag it (remember to include your namespace in Docker Hub):
docker tag 7d9495d03763 raspberryhack/wiringpi:v1 # Check docker images
Log into your Docker Hub account (and you will be asked for your password):
docker login --username=yourhubusername --email@example.com # Or for an interactive session docker login
Now, you can push the image:
docker push raspberryhack/wiringpi:v1
Go to Docker Hub and find your pushed image.