added logo and font sizes;w

src/sass/_custom-variables.scss

@@ -0,0 +1,11 @@
+
+$use-logo:                      true;
+
+$logo-image-width:              140px;
+
+$header-padding-vertical:       20px;
+
+$brand-primary:                 #444;
+
+$font-size-base:                16px;
+$font-size-large-px:            20px;