Fixed sidebar visibility bug

Add `visibility: hidden` to `.sidebar` and toggle it to `visible` when sidebar is in view. Keeps it from showing up when scrolling past the browser's viewport in Safari as well.

Fixes #31

Author: mmistakes

CHANGELOG.md

@@ -8,7 +8,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ## [1.1.2] - 2017-09-14
 
 ### Fixed
-- `/_sass/_print.scss` to reduce blank pages when printing in Chrome. [#29](https://github.com/mmistakes/jekyll-theme-basically-basic/issues/29)
+- Adjusted `/_sass/_print.scss` to reduce blank pages when printing in Chrome. [#29](https://github.com/mmistakes/jekyll-theme-basically-basic/issues/29)
+- Fixed sidebar visibility bug in Firefox and Safari by adding toggling `visibility: hidden`. [#31](https://github.com/mmistakes/jekyll-theme-basically-basic/issues/31) 
 
 ## [1.1.1] - 2017-09-06
 ### Changed

_sass/basically-basic/_sidebar.scss

@@ -10,11 +10,20 @@
   max-width: $sidebar-width;
   height: 100%;
   z-index: 50;
+  visibility: hidden;
+  -webkit-transition: visibility 0s 0.3s;
+  transition: visibility 0s 0.3s;
 
   @include breakpoint($large) {
     max-width: (1.5 * $sidebar-width);
   }
 
+  &.is--visible {
+    visibility: visible;
+    -webkit-transition: visibility 0s 0s;
+    transition: visibility 0s 0s;
+  }
+
   li {
     transform: translateX(-1rem);
     transition: all 0.5s;