Fix acceptance tests

Previously, acceptance tests were failing during the initial
installation of fixtures:

> Cloning into 'spec/fixtures/modules/puppet_agent'...
> fatal: unable to connect to github.com:
> github.com\[0: 140.82.113.4]: errno=Connection timed out

This switches to using `https` URLs for the fixtures, which allows
acceptance tests to proceed beyond that point.

Author: danielparks

.fixtures.yml

@@ -1,6 +1,6 @@
 fixtures:
   repositories:
-    facts: 'git://github.com/puppetlabs/puppetlabs-facts.git'
-    provision: 'git://github.com/puppetlabs/provision.git'
-    puppet_agent: 'git://github.com/puppetlabs/puppetlabs-puppet_agent.git'
+    facts: 'https://github.com/puppetlabs/puppetlabs-facts.git'
+    provision: 'https://github.com/puppetlabs/provision.git'
+    puppet_agent: 'https://github.com/puppetlabs/puppetlabs-puppet_agent.git'
   symlinks: []