use osfamily instead of operatingsystem to determine $gplusplus_package

This fixes the g++ package requirement for all RedHat variants.
Added tests for g++ package differences by osfamily
expose npm installed binaries via system $PATH
Merge pull request #33 from grafjo/patch-8

expose npm installed binaries via system $PATH
Merge pull request #32 from michaelmarziani/master

use osfamily instead of operatingsystem to determine $gplusplus_package
Temporary workaround for failing 1.8.7 Ruby/Travis

Rubygems broke Travis/Bundler builds on Ruby 1.8.7:

* https://github.com/travis-ci/travis-ci/issues/1793
* https://github.com/rubygems/rubygems/pull/763

This patch is a temporary workaround until rubygems is updated.
Prepare 1.6.0 release
[blacksmith] Bump version