Loop over packer bins only

And avoid looping at all if user requests
  packerio_bin_path equals packerio_install_dir.
Unarchive packer depending on installed version

Get version of possibly installed version of packer and compare
to version to be installed.
Call unarchive task only if version information seem to differ.
"Hardcode" installation directory

Hardcoding the installation directory to /opt/packerio/$VERSION
allows to only "unarchive" the distribution when required.
Install and symlink packer using handlers
ansible-packer 0.2.0