html_of_wiki version 2.1: improve user experience and reliability

Html_of_wiki v2.0 was released without formal reliability precautions and the user experience is awful. The aim for version 2.1 are:

Have a consistent command line interface such as how build, how check links or how deploy --local.
Write a test suite and integrate it in the Travis CI
Fix the different parser bugs an issues.
Implement how check links for dead link detection (cf. linkchecker).

ocsigen / html_of_wiki