docs: nit-picky documentation

* Adds nit-picky sphinx-build in travis build.

* Adds placeholder documents for the missing pages.

* Comments out all the badly documented modules.

* NOTE you can test that the documentation is fine by building
  it using: $ sphinx-build -nWE docs docs/_build/html

Signed-off-by: Yoan Blanc <yoan.blanc@cern.ch>