Add arbitrary directives to squid.conf through an attribute

Add arbitrary directives to squid.conf by providing a hash in the 'directives' attribute for the cookbook.

Example (in a wrapper cookbook)

    default['squid']['directives'] = [
        { :name => 'ignore_expect_100', :value => 'on' },
        { :name => 'acl', :value => 'BrokenButTrustedServers dstdomain brokenserver.com' },
        { :name => 'sslproxy_cert_error', :value => 'allow BrokenButTrustedServers' },
        { :name => 'sslproxy_cert_error', :value => 'deny all' }
    ]

There's no way for specifying where in squid.conf these directives go;  it was sufficient for me for the directives to be appended to the bottom of squid.conf