update css file for npm packaging

Author: okendoken

awesome-bootstrap-checkbox.css

@@ -18,7 +18,7 @@
   top: 2px;
   left: 0;
   margin-left: -1.25rem;
-  border: 1px solid rgba(0, 0, 0, 0.15);
+  border: 1px solid #ced4da;
   border-radius: 3px;
   background-color: #fff;
   transition: border 0.15s ease-in-out, color 0.15s ease-in-out; }
@@ -175,7 +175,7 @@
   top: 2px;
   left: 0;
   margin-left: -20px;
-  border: 1px solid rgba(0, 0, 0, 0.15);
+  border: 1px solid #ced4da;
   border-radius: 50%;
   background-color: #fff;
   transition: border 0.15s ease-in-out; }