fix(MdSteppers): zero height in IE (#1664)

Author: Samuell1

src/components/MdSteppers/MdSteppers.vue

@@ -357,7 +357,7 @@
       }
 
       .md-steppers-container {
-        flex-direction: column;
+        display: block;
       }
 
       .md-button-content {
@@ -373,6 +373,7 @@
       }
 
       .md-stepper {
+        flex: none;
         padding: 0;
         position: relative;