Fix #89, bug introduced earlier where all headers are black in all color themes

src/theme/book.css

@@ -12,14 +12,6 @@ body {
 .hidden {
   display: none;
 }
-a h1,
-a h2,
-a h3,
-a h4,
-a h5 {
-  color: #000;
-  pointer: cursor;
-}
 h2,
 h3 {
   margin-top: 2.5em;
@@ -323,6 +315,15 @@ h5 {
 .light pre > .result {
   margin-top: 10px;
 }
+.light .content .header:link,
+.light .content .header:visited {
+  color: #333;
+  pointer: cursor;
+}
+.light .content .header:link:hover,
+.light .content .header:visited:hover {
+  text-decoration: none;
+}
 .light .sidebar {
   background-color: #fafafa;
   color: #364149;
@@ -402,6 +403,15 @@ h5 {
 .coal pre > .result {
   margin-top: 10px;
 }
+.coal .content .header:link,
+.coal .content .header:visited {
+  color: #98a3ad;
+  pointer: cursor;
+}
+.coal .content .header:link:hover,
+.coal .content .header:visited:hover {
+  text-decoration: none;
+}
 .coal .sidebar {
   background-color: #292c2f;
   color: #a1adb8;
@@ -481,6 +491,15 @@ h5 {
 .navy pre > .result {
   margin-top: 10px;
 }
+.navy .content .header:link,
+.navy .content .header:visited {
+  color: #bcbdd0;
+  pointer: cursor;
+}
+.navy .content .header:link:hover,
+.navy .content .header:visited:hover {
+  text-decoration: none;
+}
 .navy .sidebar {
   background-color: #282d3f;
   color: #c8c9db;
@@ -560,6 +579,15 @@ h5 {
 .rust pre > .result {
   margin-top: 10px;
 }
+.rust .content .header:link,
+.rust .content .header:visited {
+  color: #262625;
+  pointer: cursor;
+}
+.rust .content .header:link:hover,
+.rust .content .header:visited:hover {
+  text-decoration: none;
+}
 .rust .sidebar {
   background-color: #3b2e2a;
   color: #c8c9db;

src/theme/stylus/general.styl

@@ -15,13 +15,6 @@ html, body {
     display: none;
 }
 
-a {
-    h1, h2, h3, h4, h5 {
-        color: black;
-        pointer: cursor;
-    }
-}
-
 h2, h3 { margin-top: 2.5em }
 h4, h5 { margin-top: 2em }
 

src/theme/stylus/themes/base.styl

@@ -34,6 +34,15 @@
     color: $fg
     background-color: $bg
 
+    .content .header:link, .content .header:visited {
+        color: $fg;
+        pointer: cursor;
+
+        &:hover {
+            text-decoration: none;
+        }
+    }
+
     .sidebar {
         background-color: $sidebar-bg
         color: $sidebar-fg