Add mod_pagespeed recipe for debian / ubuntu

- gets the latest 64bit package and installs it
- the default config file is in templates/mods/pagespeed.conf.erb
Use file_cache_path instead of /tmp/
Add attribute to handle the location of mod_pagespeed
Add warning for unsupported systems
Merge pull request #1 from zozi/COOK-2572

Add mod_pagespeed recipe for debian / ubuntu