Add support for Systemd and move to Inspec

[joestump]

Like many others we're using a version of Ubuntu that uses Systemd rather than Upstart. Attached is an update that accomplishes the following:

• Breaks up the service.rb depending on the init_package of the node.
• Converts all tests to Inspec, which is the latest testing framework from Chef.
• Adds appropriate tests for Systemd.
• Bumps CentOS in KitchenCI to 7.3. The CentOS 6.5 box is no longer available on bento and doesn't support either Upstart nor Systemd (CentOS < 7 was SysV).

It should also be noted that there's a few quirks with installing the latest NodeJS using the nodejs cookbook. That cookbook doesn't use the new 6.x and 7.x apt repositories, which leaves you with no npm and a very old version of Node. Hence the attributes to reconfigure that cookbook correctly. Additionally, you must include nodejs::npm now in your run_list if you'd like npm installed. It doesn't necessarily come installed by default.

Fixes #106 #36 #34 #35

[mheffner]

@joestump thank you for the PR, merged!

[joestump]

No problem; thanks for releasing this! 👍🏼