- updated dependency for puppetlabs/stdlib to < 7.0.0

[cspeterson]

Since I just came here to make the same PR, I'll add my justification to this one:

Here are all the stdlib functions used in the module and why it's fine to use < 7.0.0

• ensure_packages(): same
• ensure_resource(): same
• concat(): same
• empty(): deprecated as of Puppet 5.5 but replaced by builtin
• join(): deprecated as of Puppet 5.4 but replaced by builtin

also, tested and works

[ghoneycutt]

Thanks @kmarcroft and @cspeterson !!

[ghoneycutt]

Fixes #109