updated gemfile to fix ruby racer compile error in 1.9.3


Here's the error I was getting, works fine now:


    Installing therubyracer (0.9.8) with native extensions 
    Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.

            /Users/yuletide/.rvm/rubies/ruby-1.9.3-p125/bin/ruby extconf.rb 
    checking for main() in -lobjc... yes
    creating Makefile

    make
    compiling rr.cpp
    clang: warning: argument unused during compilation: '-rdynamic'
    rr.cpp:48:1: warning: control reaches end of non-void function [-Wreturn-type]
    }
    ^
    rr.cpp:151:44: warning: implicit conversion loses integer precision: 'long' to 'int' [-Wshorten-64-to-32]
        return String::New(RSTRING_PTR(value), RSTRING_LEN(value));
                                               ^~~~~~~~~~~~~~~~~~
    /Users/yuletide/.rvm/rubies/ruby-1.9.3-p125/include/ruby-1.9.1/ruby/ruby.h:674:6: note: expanded from macro 'RSTRING_LEN'
         RSTRING_EMBED_LEN(str) : \
         ^
    /Users/yuletide/.rvm/rubies/ruby-1.9.3-p125/include/ruby-1.9.1/ruby/ruby.h:670:6: note: expanded from macro 'RSTRING_EMBED_LEN'
         (long)((RBASIC(str)->flags >> RSTRING_EMBED_LEN_SHIFT) & \
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    rr.cpp:151:44: warning: implicit conversion loses integer precision: 'long' to 'int' [-Wshorten-64-to-32]
        return String::New(RSTRING_PTR(value), RSTRING_LEN(value));
                                               ^~~~~~~~~~~~~~~~~~
    /Users/yuletide/.rvm/rubies/ruby-1.9.3-p125/include/ruby-1.9.1/ruby/ruby.h:675:28: note: expanded from macro 'RSTRING_LEN'
         RSTRING(str)->as.heap.len)
                               ^
    3 warnings generated.
    compiling v8.cpp
    clang: warning: argument unused during compilation: '-rdynamic'
    compiling v8_array.cpp
    clang: warning: argument unused during compilation: '-rdynamic'
    compiling v8_callbacks.cpp
    clang: warning: argument unused during compilation: '-rdynamic'
    compiling v8_context.cpp
    clang: warning: argument unused during compilation: '-rdynamic'
    compiling v8_date.cpp
    clang: warning: argument unused during compilation: '-rdynamic'
    compiling v8_debug.cpp
    clang: warning: argument unused during compilation: '-rdynamic'
    compiling v8_exception.cpp
    clang: warning: argument unused during compilation: '-rdynamic'
    v8_exception.cpp:10:16: warning: unused variable 'stack' [-Wunused-variable]
      static void* stack[20];
                   ^
    1 warning generated.
    compiling v8_external.cpp
    clang: warning: argument unused during compilation: '-rdynamic'
    v8_external.cpp:10:9: warning: unused variable 'references' [-Wunused-variable]
      VALUE references;
            ^
    1 warning generated.
    compiling v8_function.cpp
    clang: warning: argument unused during compilation: '-rdynamic'
    v8_function.cpp:24:23: error: variable length array of non-POD element type 'Handle<v8::Value>'
        Handle<Value> argv[argc];
                          ^
    v8_function.cpp:36:23: error: variable length array of non-POD element type 'Handle<v8::Value>'
        Handle<Value> argv[argc];
                          ^
    2 errors generated.
    make: *** [v8_function.o] Error 1


    Gem files will remain installed in /Users/yuletide/.rvm/gems/ruby-1.9.3-p125/gems/therubyracer-0.9.8 for inspection.
    Results logged to /Users/yuletide/.rvm/gems/ruby-1.9.3-p125/gems/therubyracer-0.9.8/ext/v8/gem_make.out
    An error occured while installing therubyracer (0.9.8), and Bundler cannot continue.
    Make sure that `gem install therubyracer -v '0.9.8'` succeeds before bundling.