Minor fixes for site (disable mathjax, fix appendix header)

doc/sphinx/book/app_b_proctitle.rst

@@ -2,7 +2,7 @@
 .. highlight:: lua
 
 -------------------------------------------------------------------------------
-                        Appendix B. List of error codes
+                        Appendix B. Process title
 -------------------------------------------------------------------------------
 
 Linux and FreeBSD operating systems allow a running process to modify its title,

doc/sphinx/book/index.rst

@@ -3,6 +3,7 @@
 -------------------------------------------------------------------------------
 
 .. toctree::
+    :maxdepth: 2
 
     intro
     box/index

doc/sphinx/conf.py

@@ -31,7 +31,6 @@ sys.path.insert(0, os.path.abspath('.'))
 
 extensions = [
     'sphinx.ext.todo',
-    'sphinx.ext.mathjax',
     'sphinx.ext.ifconfig',
     'ext.filters',
     'ext.lua'