Multiple UI Improvements (#4712)

* Multiple UI Improvements

* Reverting modal animation

webapp/sass/components/_mentions.scss

@@ -21,6 +21,11 @@
     width: 100%;
     z-index: 101;
 
+    .fa-user {
+        position: relative;
+        top: -1px;
+    }
+
     .mention--align {
         @include clearfix;
         text-overflow: ellipsis;

webapp/sass/components/_popover.scss

@@ -17,6 +17,7 @@
     }
 
     .popover-title {
+        @include border-radius(0);
         background: alpha-color($black, .05);
         max-width: 100%;
         overflow: hidden;