Merge pull request #20 from ypcs/master

Merge recent development.
Fixed Markdown syntax.
Removed TODO, already completed.
Added details for 13.12.24.
Added timeline.
Added more details about version naming.
Improved Markdown formatting.
Added missing parenthesis.
How to create codename.
Details for 2.0.
Added details about packages. Install linux-headers for improved VirtualBox support.
Added information about packages.
Added better details about Iceweasel.
Use  instead of .
Separated package plymouth-themes-digabi from digabi-customization.
Ignore digabi.png (logo).
Separated package digabi-backgrounds from digabi-customizations.
Ignore proprietary content.
Added script for resizing background images using rsvg.
Updated image resizing script.