[community] Use left-side nav, restructure page.

This update to the community page is a prototype of doing
something similar with other pages on the site, notably the
documentation index page.
Fix community's page sidebar on mobile
Use sidebar navigation on documentation page

This commit is a first iteration of a reorganization of the documentation
page.
Use definition style on documentation page

Replace the old quotes style (gray bars) with the new definiton
(no gray bars) style for text blocks.
Add 3 publications to the documentation page
Convert the publications page to the new style

Change the old quote style to the new style.
Merge pull request #49 from fracek/documentation_rework

Documentation rework
Reorder documentation's sections

1. Cheat Sheets
2. Learning Dylan
3. References
4. Articles
5. Publications
6. For Open Dylan Developers
7. Archived Documentation
Merge pull request #50 from fracek/reorder_doc

Reorder documentation's sections
Reflect new name of the Getting Started document.
Link to new getting-started-cli document.
Update link to point to new Sphinx site.
Replace GSOC-2012 idea list with new wiki list.
Fix typo, spotted by Marc Feeley.
Update Boehm GC Ubuntu installation tip.
Merge pull request #54 from micrypt/patch-1

Update Boehm GC Ubuntu installation tip.
Fix internal hyperlink references.
Add contributing section, rework development.

I also removed the link to Trello as we're tracking that info
in the wiki now.
Try naming 'Community' 'Participate' instead.
Announcement of the hack-a-thon.