Convert @processorcount to string

I'm getting this error when `stringify_facts = false`:

```
Error: Could not retrieve catalog from remote server: Error 400 on SERVER: Failed to parse template memcached/memcached_sysconfig.erb:
  Filepath: /etc/puppet/environments/production/modules/memcached/templates/memcached_sysconfig.erb
  Line: 18
  Detail: can't convert Fixnum into String
 at /etc/puppet/environments/production/modules/memcached/manifests/init.pp:78 on node v-wh1.vagrant
```

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btw, thanks for all of your great work @saz !