Compile error on Ubuntu 15.04

[FrenchDilettante]

Hi there!

I tried to compile node-qt locally and got the following error:

../src/QtWidget/qpushbutton.cc:34:5: error: no matching function for call to ‘QObject::connect(QPushButton*&, void (QAbstractButton::*)(bool), QPushButtonWrap::QPushButtonWrap(const v8::Arguments&)::<lambda()>)’

Which apparently is because it wasn't compiling with the c+11 flag. I could make it work locally by changing binding.gyp line 37:

'cflags': [
    '-std=c++11 <!@(pkg-config --cflags Qt5Core Qt5Gui Qt5Widgets Qt5Multimedia)'
],

But I don't know much about Node C++ wrapper, so I'm not sure if this is a reliable fix.