[Test] Add integration tests for complex and larger variety of webpages

[oliviermills]

In tweaking and growing the html clean up and html-to-md. I highly recommend adding integration tests using either live webpages (to test also the get/network and dynamic websites) OR at least saved html pages with complex layout (and bad html, especially for the html clean up.

• Find a list of pages to use as test suite with a vareity of layouts
• Add the integration tests

[nickscamara]

• Add more specific tests like h1 -> #
• Get a list of website -> markdown small dataset

[rafaelsideguide]

Closing this one (related to #118)