This fixes the remaining Python 3 syntax errors, so re-enable compileall
for contrib/ again.

renamed plugins to contrib (they are not really plugins)
rewrote README.md to reflect new usage
added new dir to setup.py so it gets copied with installation, in views
of making using inventory scripts easier in teh future

default to private ip if the instance doesn't have a public ip assigned. (causes list index out of range error otherwise)

This fix resolves an issue on EL6 systems where there may be multiple versions
of pycrypto installed.  EPEL provides both `python-crypto` and
`python-crypto2.6`.  These packages are co-installable.  However, modules
importing the `Crypto` library must specify which version to use, otherwise the
default will be used.

This change follows the same pattern established in `bin/ansible` for
specifying python library requirements.

Fix https://github.com/ansible/ansible/issues/9948

In order to simplify the workflow with the GCE modules, it's now
possible to add the parameters and project name as arguments to the
various GCE modules.

The inventory plugin also returns the IP of the host in
`ansible_ssh_host` so that you don't have to specify IPs into the
inventory file.

Some update to the documentation are also added.

Closes #5583.