docs: integration to single page

* Improves PEP8 and PEP257 of all files.

* Integrates documentation on a single page.

* Adds tests for strict Sphinx documentation build and PEP257.

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
menu: additional keyword arguments store

* Stores additional keyword arguments as `MenuItem` attributes.

Co-authored-by: Jiri Kuncar <jiri.kuncar@cern.ch>
Signed-off-by: Eirini Psallida <eirini.psallida@cern.ch>
tests: testing the keyword arguments of Menu

* Tests the keyword arguments and if they cannot be overriden.

Signed-off-by: Eirini Psallida <eirini.psallida@cern.ch>
docs: versionchanged for kwargs argument

* Adds `versionchanged` for kwargs argument.  (PR #20)

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
Reviewed-by: Tibor Simko <tibor.simko@cern.ch>
docs: documentation of missing methods

* Adds documentation for missing methods, making `run-tests.sh` to pass
  again.

Signed-off-by: Tibor Simko <tibor.simko@cern.ch>
Co-authored-by: Jiri Kuncar <jiri.kuncar@cern.ch>
setup: richer `MANIFEST.in`

* Enriches `MANIFEST.in` as per recommendations from `check-manifest`.

Signed-off-by: Tibor Simko <tibor.simko@cern.ch>
Flask-Menu v0.2.0

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
Signed-off-by: Tibor Simko <tibor.simko@cern.ch>