Added activity history to to all entities. Fixes #12

database/migrations/2015_08_16_142133_create_activities_table.php

@@ -0,0 +1,36 @@
+<?php
+
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Database\Migrations\Migration;
+
+class CreateActivitiesTable extends Migration
+{
+    /**
+     * Run the migrations.
+     *
+     * @return void
+     */
+    public function up()
+    {
+        Schema::create('activities', function (Blueprint $table) {
+            $table->increments('id');
+            $table->string('key');
+            $table->text('extra');
+            $table->integer('book_id')->indexed();
+            $table->integer('user_id');
+            $table->integer('entity_id');
+            $table->string('entity_type');
+            $table->timestamps();
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     *
+     * @return void
+     */
+    public function down()
+    {
+        Schema::drop('activities');
+    }
+}