Merge PR #19, Props @JiveDig. Squashed commit of the following:

commit 03dce5fc6a31107bbe67d2330398952f341c68b5
Merge: c62d4b7 3c358ec
Author: Justin Sternberg <[email protected]>
Date:   Wed Jun 7 11:18:36 2017 -0400

    Merge branch 'master' into JiveDig-master

commit c62d4b7
Author: Mike Hemberger <[email protected]>
Date:   Wed Jun 7 10:20:14 2017 -0400

    More consistent checkbox field styling

Author: jtsternberg

css/shortcode-button.css

@@ -37,8 +37,9 @@
 .ui-dialog .cmb-type-checkbox .cmb-td {
 	padding: 1.2em 0 0 0;
 }
-.ui-dialog .cmb-type-checkbox .cmb-th {
-	width: 300px;
+.ui-dialog .cmb-type-checkbox .cmb2-metabox-description {
+	color: inherit;
+	font-style: inherit;
 }
 .ui-dialog .cmb-th + .cmb-td {
 	float: none;