styleguide: initial release of style guide

* Creates new `styleguide` module and sets up the handler under
  `/style-guide`.

Signed-off-by: Georgios Kokosioulis <georgios.kokosioulis@cern.ch>
styleguide: addition of libraries

Signed-off-by: Georgios Kokosioulis <georgios.kokosioulis@cern.ch>
styleguide: initial release of all components

Signed-off-by: Georgios Kokosioulis <georgios.kokosioulis@cern.ch>