Update stylesheets in session files and add new syntax highlighting theme

Author: jevillanueva

content/sesion01/index.html

@@ -6,7 +6,7 @@
     <title>Sesión 01 OOP - Python Study Group</title>
     <link rel="stylesheet" href="../../dist/reveal.css">
     <link rel="stylesheet" href="../../dist/theme/black.css" id="theme">
-    <link rel="stylesheet" href="../../plugin/highlight/dracula.css">
+    <link rel="stylesheet" href="../../plugin/highlight/atom-one-dark-reasonable.css">
     <link rel="stylesheet" href="../../plugin/pointer/pointer.css" />
     <link rel="stylesheet" href="../custom.css">
 </head>

content/sesion02/index.html

@@ -6,7 +6,7 @@
     <title>Sesión 02 OOP - Python Study Group</title>
     <link rel="stylesheet" href="../../dist/reveal.css">
     <link rel="stylesheet" href="../../dist/theme/black.css" id="theme">
-    <link rel="stylesheet" href="../../plugin/highlight/dracula.css">
+    <link rel="stylesheet" href="../../plugin/highlight/atom-one-dark-reasonable.css">
     <link rel="stylesheet" href="../../plugin/pointer/pointer.css" />
     <link rel="stylesheet" href="../custom.css">
 </head>