Add basic print styles

- Hide menu, social share buttons, and ads on print
- Close #191

assets/css/main.scss

@@ -25,4 +25,5 @@ sitemap: false
 @import "page";
 @import "vendor/font-awesome/font-awesome";
 @import "vendor/magnific-popup/magnific-popup";
-//@import "vendor/google/fonts";
+//@import "vendor/google/fonts";
+@import "print";