Remove install.md due to installation.md

All content from install.md is already mentioned in installation.md.

In order to reduce duplicated content, the orphaned file is removed.
Integrate install.md & improve overall structure
Fix formating issues and add more structure
Split instructions for vagrant into sub-files

Update the instructions for creating a new Veewee definition.

Uses Ubuntu 12.10.
Add more instructions / todos for contributing
Improve definition description and file tree

This corrects some typos and add more descriptive introduction.
Add CONTRIBUTE file

See https://github.com/blog/1184-contributing-guidelines for details
Add cross reference to contribute.md

In order to avoid duplicated content I reference to another document
Fix small typo in headline
Fix typo in Pro Tip
Rename 'myubuntu' to 'myubuntubox'

In order to be more consistent in naming the box I changed the name to the one used in vagrant.md.

The name can be improved / shortened but first it has to be consistent.
Smaller format / typo fixes
Update CONTRIBUTION guidelines
Remove contribute.md in favor of CONTRIBUTE.md
Elaborate RVM instructions
Add moar links
Remove hardcoded links to veewee repo

Now links also work in forked repos.
Fix markup typo and add link to customize.md
Add introduction for definitions
Fix link to customize.md