light theme: initial release

Initial release of light octopress theme, inspired by
http://aijazansari.com/2012/08/27/how-to-customize-octopress-theme/
light theme: ligher highlight/pre boxes
light theme: "Read On" arrow direction
light theme: positive list indentation in posts

Adapts list indentation in blog posts to be indented inside the page,
as is usual one the web.  (Even though the original Octopress theme would
"negative-indent" list items so that item bullets would start in left
margin of the page blank already.)
templates/archives: do now show "posts" category

* Since I'm using one category only, do not show it in the archives
  template since it is only consuming space.

Signed-off-by: Tibor Simko <tibor.simko@cern.ch>
templates/sidebar: hide categories

* Hide "Categories" box in the sidebar since I'm using tags facility
  only for the time being.

Signed-off-by: Tibor Simko <tibor.simko@cern.ch>
sass/sidebar: no list item borders

Signed-off-by: Tibor Simko <tibor.simko@cern.ch>
sass/base/theme: no dotted line around text

Signed-off-by: Tibor Simko <tibor.simko@cern.ch>
templates/social: lowercase atom/rss

Signed-off-by: Tibor Simko <tibor.simko@cern.ch>