paper: fix btn-group margin, closes #400

paper/_bootswatch.scss

@@ -86,6 +86,24 @@
   }
 }
 
+.btn-group {
+  .btn + .btn,
+  .btn + .btn-group,
+  .btn-group + .btn,
+  .btn-group + .btn-group {
+    margin-left: 0;
+  }
+
+  &-vertical {
+    > .btn + .btn,
+    > .btn + .btn-group,
+    > .btn-group + .btn,
+    > .btn-group + .btn-group {
+      margin-top: 0;
+    }
+  }
+}
+
 // Typography =================================================================
 
 body {

paper/bootstrap.css

@@ -6781,6 +6781,18 @@ button.close {
 .btn-default.disabled {
   border: 1px solid #eeeeee;
 }
+.btn-group .btn + .btn,
+.btn-group .btn + .btn-group,
+.btn-group .btn-group + .btn,
+.btn-group .btn-group + .btn-group {
+  margin-left: 0;
+}
+.btn-group-vertical > .btn + .btn,
+.btn-group-vertical > .btn + .btn-group,
+.btn-group-vertical > .btn-group + .btn,
+.btn-group-vertical > .btn-group + .btn-group {
+  margin-top: 0;
+}
 body {
   -webkit-font-smoothing: antialiased;
   letter-spacing: .1px;

paper/bootswatch.less

@@ -86,6 +86,24 @@
   }
 }
 
+.btn-group {
+  .btn + .btn,
+  .btn + .btn-group,
+  .btn-group + .btn,
+  .btn-group + .btn-group {
+    margin-left: 0;
+  }
+
+  &-vertical {
+    > .btn + .btn,
+    > .btn + .btn-group,
+    > .btn-group + .btn,
+    > .btn-group + .btn-group {
+      margin-top: 0;
+    }
+  }
+}
+
 // Typography =================================================================
 
 body {