fix(checkbox): adds ability to click links within checkbox

Closes #852

Author: Robert Messerle

src/components/checkbox/checkbox.scss

@@ -130,7 +130,6 @@ md-checkbox {
     display: inline-block;
     vertical-align: middle;
     white-space: normal;
-    pointer-events: none;
     user-select: text;
 
     span {