Update Texinfo with some variables

Automake provides us variables with the version of the program,
when it was generated the documentation... these variables can be
used in the program for making it more flexible.

.gitignore

@@ -38,7 +38,10 @@ src/chip8/chip8
 .cproject
 .project
 .settings/
+
+# Texinfo files
 doc/texinfo.tex
 doc/version.texi
 doc/stamp-vti
 doc/mdate-sh
+doc/chip8.info

doc/chip8.texi

@@ -23,13 +23,14 @@ in the section entitled "GNU Free Documentation License".
 @titlepage
 @title CHIP-8
 @subtitle Package manual
-@subtitle version v0.2.0
+@subtitle version @value{VERSION}
+@subtitle @value{UPDATED-MONTH}
 @author Dani Rodr@'iguez
 
 @c Print copyright information
 @page
 @vskip 0pt plus 1fill
-This is the user manual for version v0.2.0 of CHIP-8 software package.
+This is the user manual for version @value{VERSION} of CHIP-8 software package.
 To check for updates, please visit @uref{http://github.com/danirod/chip8}.
 
 @insertcopying
@@ -42,7 +43,7 @@ To check for updates, please visit @uref{http://github.com/danirod/chip8}.
 @ifnottex
 @node Top
 @top CHIP-8 Package manual
-This is the user manual for version v0.2.0 of CHIP-8 software package.
+This is the user manual for version @value{VERSION} of CHIP-8 software package.
 To check for updates, please visit @uref{http://github.com/danirod/chip8}.
 @end ifnottex