Presentations page without database

[stevelaskaridis]

Created a 3rd page in the webpage where the presentations available from past meetups are presented to the user.

More specifically:

• Added the page, creating a new view (app/views/presentations/index.html.erb)
• Changed the layout view to provide access to the new view
• Minor addition in custom.css
• Created a controller for the new view (app/controllers/presentations_controller.rb)
  • support for sorting
• Added the relevant route
• Created model Presentation class (app/models/presentation.rb)

Concerning pull request #50, the changes that were discussed were applied.

Screenshot preview:

[stevelaskaridis]

@petros, @xarisd, your feedback would be greatly appreciated ...

[xarisd]

Guys I was busy with doctors and a funeral. I won't be available till next week.
@stevelaskaridis sorry for not replying sooner...