support Software Collections

Red Hat (and derivatives) can access node.js via [Software Collections](https://access.redhat.com/documentation/en-US/Red_Hat_Software_Collections/1/html/1.1_Release_Notes/index.html). This pull requests adds initial Software Collections support to puppetlabs-nodejs.

There are a couple of important caveats to this PR:
* management of the Software Collections yum repository is not controlled through this module.
* this PR is hard-coded to use nodejs010.  If SCL releases a new version of nodejs, it'll require re-work on this module.
* If the optional `$scl_enable` parameter is passed to init.pp, a symlink will be created from `/opt/rh/nodejs010/enable` to `/etc/profile.d/nodejs.sh`.  Users of non-sh-compatible shells will not benefit from this. Such users are on their own.
* the custom `npm` provider included in this module has not been updated.  This means that the `npm` command will **not** work on the first invocation of this module.  Users will need to apply this module once to install the SCL packages, and then apply this module a second time in order for the `npm` command to work as expected.