Fix for mavericks / homebrew re #87

Basically just copying solution from https://github.com/mshick/node-protobuf/commit/a071e792065770c9e7372b409d37f295f9473ece

Actually have no idea _why_ this works - assume there's some intricacies with xcode on mavericks.

binding.gyp

@@ -33,6 +33,9 @@
           # cflags on OS X are stupid and have to be defined like this
           'xcode_settings': {
             'OTHER_CFLAGS': [
+              "-mmacosx-version-min=10.7",
+              "-std=c++11",
+              "-stdlib=libc++",
               '<!@(pkg-config --cflags opencv)'
             ]
             , "GCC_ENABLE_CPP_RTTI": "YES"