Added smarter page finding so changing the page name does not break old urls

Added page & book slug history to revisions so they can be looked up if a page is not found.

database/migrations/2016_02_25_184030_add_slug_to_revisions.php

@@ -0,0 +1,35 @@
+<?php
+
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Database\Migrations\Migration;
+
+class AddSlugToRevisions extends Migration
+{
+    /**
+     * Run the migrations.
+     *
+     * @return void
+     */
+    public function up()
+    {
+        Schema::table('page_revisions', function (Blueprint $table) {
+            $table->string('slug');
+            $table->index('slug');
+            $table->string('book_slug');
+            $table->index('book_slug');
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     *
+     * @return void
+     */
+    public function down()
+    {
+        Schema::table('page_revisions', function (Blueprint $table) {
+            $table->dropColumn('slug');
+            $table->dropColumn('book_slug');
+        });
+    }
+}