Localize strings in copypaste SOCKS sample

ran grunt test

There is a drop down that switches the language between Italian and English.
After migrating the popup to Polymer I can try a RTL language.
So, rather than a separate rule for this one folder let's add a `symlink:thirdParty` rule to this Gruntfile, just like uproxy-lib's:
https://github.com/uProxy/uproxy-lib/blob/dev/Gruntfile.coffee#L96

Bug me if this doesn't work.