Install couchbase from package without curl

This allows the installation of couchbase without having to download
couchbase on every node. This change is intended for users that have an
internal repository serving up their .deb files
change curl download location from /tmp to /opt

This is because the /tmp directory gets wiped on every reboot, when a
couchbase node is rebooted the first time puppet runs it will download
the package again. Not ideal.
Add default to install_method
Merge pull request #10 from zxjinn/kelvin/install_from_package

zxjinn/install from package