Improve round corners on block input and output

assets/css/lesson.scss

@@ -32,6 +32,7 @@ $color-testimonial: #fc8dc1 !default;
   color: $color;
   border-left: solid 5px $color;
   margin-bottom: 0px;
+  border-radius: 4px 0 0 4px;
 }
 
 .error  { @include cdSetup($color-error); }
@@ -45,6 +46,18 @@ $color-testimonial: #fc8dc1 !default;
 .r      { @include cdSetup($color-source); }
 .sql    { @include cdSetup($color-source); }
 
+.error pre,
+.output pre,
+.source pre,
+.bash pre,
+.make pre,
+.matlab pre,
+.python pre,
+.r pre,
+.sql pre {
+  border-radius: 0 4px 4px 0;
+}
+
 //----------------------------------------
 // Specialized blockquote environments for learning objectives, callouts, etc.
 //----------------------------------------