Improve the contrast between the background and text (#74)

Change text color from `#c6cddb` to `#e8eef2` in order to improve accessibility. Hermit theme now passes WCAG level AAA (contrast > 7.0).

assets/scss/_predefined.scss

@@ -1,7 +1,7 @@
 // Colors
 //
 $theme: #018574;
-$text: #c6cddb;
+$text: #e8eef2;
 $light-grey: #494f5c;
 $dark-grey: #3B3E48;
 $highlight-grey: #7d828a;