Add instructions to make minikube's docker env available during 'make…

… docker_build' (#586)

Minikube uses a separate docker daemon from the normal system docker
daemon, so you need to tell your shell how to access the minikube docker
daemon. Otherwise when the Task runs it fails immediately because it
tries to pull from Dockerhub.

This also removes a redundant "to" in the following sentence.

rsts/user/getting_started/create_first.rst

@@ -105,9 +105,10 @@ Interacting with Flyte
 
 Flyte fulfills tasks using docker images. You'll need to build a docker image from this code before it can run in Flyte. The repo has a make target to build the docker image for you ::
 
+  eval $(minikube -p minikube docker-env)  # If using the flyte sandbox via minikube
   make docker_build
 
-If you have the flyte sandbox installed on your local machine, the image will be accessible to to your Flyte system. If you're running a remote Flyte instance, you'll need to upload this image to a remote registry such as Dockerhub, Amazon ECR, or Google Container Registry, so that it can be used by the Flyte system. 
+If you have the flyte sandbox installed on your local machine, the image will be accessible to your Flyte system. If you're running a remote Flyte instance, you'll need to upload this image to a remote registry such as Dockerhub, Amazon ECR, or Google Container Registry, so that it can be used by the Flyte system.
 
 To upload to a remote registry (or even local registry), use ::