Update lemon-graph formula to match version 1.3.1 of lemon in COIN-OR.

In COIN-OR Lemon webpage (http://lemon.cs.elte.hu/trac/lemon/wiki/Downloads) there's already a new version for lemon (1.3.1) so the brew formula should be updated as well. Also the ticket http://lemon.cs.elte.hu/trac/lemon/ticket/471 is closed for this new version so the fragment code:

```ruby  
fails_with :clang do
  # http://lemon.cs.elte.hu/trac/lemon/ticket/471
  build 500
  cause <<-EOS.undent
    dependent using declaration resolved to type without 'typename'
    EOS
end
```

is not needed anymore.