fix menu button tooltip style & set default font to buttons

browser/main/SideNav/SideNav.styl

@@ -78,28 +78,30 @@
     width 44px - 1
     text-align center
     &:hover .top-menu-label
-      width 100px
+      transition opacity 0.15s
+      opacity 1
   .top-menu-label
     position fixed
     display inline-block
-    height 34px
+    height 30px
     left 44px
-    width 0
+    padding 0 10px
-    margin-top -5px
+    margin-top -7px
+    opacity 0
     margin-left 0
     overflow hidden
     background-color $ui-tooltip-backgroundColor
     z-index 10
     color white
-    line-height 34px
+    line-height 30px
-    border-top-right-radius 5px
+    border-top-right-radius 2px
-    border-bottom-right-radius 5px
+    border-bottom-right-radius 2px
-    transition width 0.15s
     pointer-events none
+    font-size 12px
   .menu-button, .menu-button--active
-    width 44px - 1
     text-align center
     &:hover .menu-button-label
+      transition opacity 0.15s
       opacity 1
   // TODO: extract tooltip style to a mixin
   .menu-button-label
@@ -117,7 +119,6 @@
     line-height 34px
     border-top-right-radius 2px
     border-bottom-right-radius 2px
-    transition opacity 0.15s
     pointer-events none
     opacity 0
     font-size 12px

browser/styles/finder/index.styl

@@ -18,7 +18,7 @@ body
   height 100%
   overflow hidden
 button, input
-  font-family "Lato"
+  font-family DEFAULT_FONTS
 
 .Finder
   absolute top bottom left right