Remove deprecated variable access (introduced in Puppet v3.2.x)

When running this module under Puppet 3.2.x (in my case 3.2.4), you'll get set of warnings.
Using variables in templates without '@' has been deprecated, and as of 3.2.x

    Warning: Variable access via 'logfile' is deprecated. Use '@logfile' instead. template[/tmp/vagrant-puppet/modules-0/memcached/templates/memcached.conf.erb]:10
    (at /tmp/vagrant-puppet/modules-0/memcached/templates/memcached.conf.erb:10:in `block in result')
    Warning: Variable access via 'max_memory' is deprecated. Use '@max_memory' instead. template[/tmp/vagrant-puppet/modules-0/memcached/templates/memcached.conf.erb]:19
    (at /tmp/vagrant-puppet/modules-0/memcached/templates/memcached.conf.erb:19:in `block in result')
    Warning: Variable access via 'listen_ip' is deprecated. Use '@listen_ip' instead. template[/tmp/vagrant-puppet/modules-0/memcached/templates/memcached.conf.erb]:31
    (at /tmp/vagrant-puppet/modules-0/memcached/templates/memcached.conf.erb:31:in `block in result')
    Warning: Variable access via 'tcp_port' is deprecated. Use '@tcp_port' instead. template[/tmp/vagrant-puppet/modules-0/memcached/templates/memcached.conf.erb]:34
    (at /tmp/vagrant-puppet/modules-0/memcached/templates/memcached.conf.erb:34:in `block in result')
    Warning: Variable access via 'udp_port' is deprecated. Use '@udp_port' instead. template[/tmp/vagrant-puppet/modules-0/memcached/templates/memcached.conf.erb]:37
    (at /tmp/vagrant-puppet/modules-0/memcached/templates/memcached.conf.erb:37:in `block in result')
    Warning: Variable access via 'user' is deprecated. Use '@user' instead. template[/tmp/vagrant-puppet/modules-0/memcached/templates/memcached.conf.erb]:41
    (at /tmp/vagrant-puppet/modules-0/memcached/templates/memcached.conf.erb:41:in `block in result')
    Warning: Variable access via 'max_connections' is deprecated. Use '@max_connections' instead. template[/tmp/vagrant-puppet/modules-0/memcached/templates/memcached.conf.erb]:44
    (at /tmp/vagrant-puppet/modules-0/memcached/templates/memcached.conf.erb:44:in `block in result')
    Warning: Variable access via 'processorcount' is deprecated. Use '@processorcount' instead. template[/tmp/vagrant-puppet/modules-0/memcached/templates/memcached.conf.erb]:47
    (at /tmp/vagrant-puppet/modules-0/memcached/templates/memcached.conf.erb:47:in `block in result')