d1c2ec3 added use_stub_resolver as a
parameter but there's a mismatch between the code and documentation.
While in practice /var/run is a symlink to /run and the mismatch doesn't
really matter, it's better to have them match to avoid confusion.

* Drop Puppet 4 and 5 support

This picks version 6.1.0 as a new lower bound since that contains code
to automatically run daemon-reload if needed. Versions 4 and 5 are EOL.

* Drop daemon-reload code

Since Puppet 6.1.0 it's no longer needed to run daemon-reload manually
when restarting a service. That means it's possible to drop this code.

* Implement a workaround for PUP-9473.

Prior to this commit, the follow code did not suffer from PUP-9473:

    systemd::unit_file { 'myservice.service':
      ensure => absent,
      active => true,
    }

That's because the module considers that an invalid state and fails to
compile.

The follow code did trigger the bug:

    systemd::unit_file { 'myservice.service':
      ensure => absent,
    }

    service { 'myservice':
      ensure  => running,
      require => Systemd::Unit_file['myservice.service'],
    }

That's precisely what happens when a module switches from a
module-provided unit file to a package-provided unit file.

97dd16f was a breaking change. Bumping
the version helps consuming modules to make a distinction with the
following code:

    $metadata = load_module_metadata('systemd')
    if SemVer($metadata['version']) >= SemVer('3.0.0') {}

My use cases is:

    systemd::unit_file { 'myservice.socket':
      content => file('mymodule/myservice.socket'),
      enable  => true,
      active  => true,
    }
    systemd::unit_file { 'myservice.service':
      content => file('mymodule/myservice.service'),
      enable  => true,
      active  => true,
    }
    $metadata = load_module_metadata('systemd')
    if SemVer($metadata['version']) >= SemVer('3.0.0') {
      Systemd::Unit_file['myservice.socket'] -> Systemd::Unit_file['myservice.service']
    }

This allows me to maintain Puppet 5 support for a bit longer while also
working with the latest version.

… testing (#183)

* metadata: allow Puppet 7

* .travis.yml: remove Puppet 5, add Puppet 7

Puppet 5 support was dropped in #171, so no need to test with it
anymore.

* release 3.0.0

* Update CHANGELOG.md

Co-authored-by: Raphaël Pinson <github+aem1eeshi1@raphink.net>