With this change the documentation instructs Windows users
to work within the Docker Quickstart Terminal rather than
Git Bash which does not work for Windows 10.
This change also adds a note to the first curl command to
address the recurrent problem with Windows users reporting
failure due to using an outdated version of curl.

Patch-set #2: added a piece about installing npm grpc based
on users reporting this was necessary.

Change-Id: I95e7caeddc43e48f107955018aced112893ca540
Signed-off-by: Arnaud J Le Hors <lehors@us.ibm.com>