Add missing flags for OS X 10.9 & node 0.11

I get this error on OS X 10.9 Mavericks with node 0.11
```
/Users/luigy/code/test/node_modules/serialport/node_modules/bindings/bindings.js:83
        throw e
              ^
Error: dlopen(/Users/luigy/code/test/node_modules/serialport/build/Release/serialport.node, 1): Symbol not found: ___CFConstantStringClassReference
  Referenced from: /Users/luigy/code/test/node_modules/serialport/build/Release/serialport.node
  Expected in: dynamic lookup

    at Module.load (module.js:349:32)
    at Function.Module._load (module.js:305:12)
    at Module.require (module.js:357:17)
    at require (module.js:373:17)
    at bindings (/Users/luigy/code/test/node_modules/serialport/node_modules/bindings/bindings.js:76:44)
    at Object.<anonymous> (/Users/luigy/code/test/node_modules/serialport/serialport.js:6:44)
    at Module._compile (module.js:449:26)
    at Object.Module._extensions..js (module.js:467:10)
    at Module.load (module.js:349:32)
    at Function.Module._load (module.js:305:12)
```