Ionic 2 responsive grid

Question

How can I make a responsive grid in Ionic 2? Ionic 1 supported reserved classes like responsive-md or responsive-sm that made grids responsive, but

Answer 1

Update for Ionic 2, Ionic 3+:

Ionic now have an amazing grid system base on flexbox css. You can see in the docs.
To use it, just simple like that:

  
     //This col will take 3/12 = 25% width;
     //This col will take 4/12 = 33.33% width;
           //This col will take the rest of width;