Errors when enabling strict_variables

[Joris-van-der-Wel]

This module seems to use three global variables which puppet 4 will complain about if strict_variables is true:

• http_proxy
• https_proxy
• schedule (manifests/fetch.pp:99)

As a workaround I have to add the following to site.pp:

$http_proxy = undef
$https_proxy = undef
$schedule = undef

Related to #45

[carlossg]

see #61