example_01/access_machine.py: Improve messaging a bit.
configure.py: Use os.path.expanduser

so that stuff like:

   ~/.ssh/devops.pem

works.
Merge pull request #43 from msabramo/configure.py_expanduser

configure.py: Use os.path.expanduser
Merge pull request #45 from msabramo/example_01_improve_messaging

example_01/access_machine.py: Improve messaging a bit.
configure.py: Make messaging not quite so specific to Amazon EC2

pem keys for example are not specific to Amazon. I am using one to
connect to an OpenStack VM for example.
configure.py: Prompt for user but default to "ec2-user"
src/example_01/access_machine.py: generalize so we can use a remote_user
other than "ec2-user" by reading it from ansible.cfg