Wrote 'The Big picture'
English fixes
Fixed comments
Created 'The Model'
Fixed ending of first chapter
Created 3th chapter: 'The router'
Fixed comments
Created Third Party Bundles chapter
Finished Quick Tour
Fixed link
Applied comments from @dbu
Added image
Made Quick Tour 1.1 ready
Merge pull request #358 from symfony-cmf/start_quick_tour

[WIP] The Quick Tour