Refactor options page and optimize for mobile view

Change-Id: I7586e407c80e804b567d645e11e31306a1bd1f90
diff --git a/src/options.css b/src/options.css
index e754e14..46961a2 100644
--- a/src/options.css
+++ b/src/options.css
@@ -1,3 +1,8 @@
+.option {
+  margin: 4px 0;
+  line-height: 1.8em;
+}
+
 .help {
   cursor: help;
   border-bottom: dashed 1px gray;