Move padding to splash element

Having it in the nav was causing issues with positioning the banner, as evidenced by the teacher banner’s `-20px` setting

src/components/teacher-banner/teacher-banner.scss

@@ -7,7 +7,7 @@
 
     &.title-banner {
         transition: none;
-        margin-bottom: 20px;
+        margin-bottom: 0;
         text-align: left;
 
         h3,

src/views/splash/splash.jsx

@@ -366,7 +366,7 @@ var Splash = injectIntl(React.createClass({
                 {this.props.permissions.educator ? [
                     <TeacherBanner key="teacherbanner" messages={messages} />
                 ] : []}
-                <div key="inner" className="inner">
+                <div key="inner" className="inner mod-splash">
                     {this.props.session.status === sessionActions.Status.FETCHED ? (
                         this.props.session.session.user ? [
                             <div key="header" className="splash-header">

src/views/splash/splash.scss

@@ -1,5 +1,13 @@
 @import "../../frameless";
 
+#view {
+    padding: 0;
+}
+
+.inner.mod-splash {
+    margin-top: 20px;
+}
+
 .splash {
     .splash-header {
         display: flex;
@@ -33,10 +41,6 @@
         }
     }
 
-    .teacher-banner {
-        margin-top: -20px;
-    }
-
     .box {
         margin-bottom: 20px;
     }