Add slideshow carousel with placeholder image

Just added a slideshow carousel to the landing page. I have added a
placeholder image that is used for now.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Add exists function for jQuery elements

In order to implement the namespace differentiation between the
JavaScript files I have added an exists function which I can use
instead of .length > 0. Also added a margin between navigation
pills and table on the repository page.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Activate the navigation tabs dynamically

I have added a helper to dynamically set the active class for the
navigation tabs in the header.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Add eager load method for metric classes

So far it was an unsolved problem to load the metric classes after file
change due to wipe per request. The only solution I found is to load all
the files with the Ruby load directive if the code is run in development
environment.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>