Update importer documentation

Dependencies were not the good one, wordpress importer needs BeautifulSoup4 and lxml
Markdown summary should not include content footnote

Markdown instance carries state for subsequent uses. Content
and summary parsing is done with the same instance. Since
footnotes are processed with an extension and stored as state,
content footnote is duplicated for summary.

This PR adds a ``.reset()`` call before summary parsing to clear
the state. It also adds a test case with footnotes.
Merge pull request #885 from avaris/markdown-summary-footnote

Markdown summary should not include content footnote
Merge pull request #881 from ben2367/patch-1

Update importer documentation
adhere to PEP8 coding standards
Merge pull request #888 from dominiqueplante/pep8-setup

adhere to PEP8 coding standards
adhere to pep8
Merge pull request #890 from dominiqueplante/pep8-content

adhere to pep8
Updated pelican.server not started error message.
Merge pull request #891 from mrshu/patch-1

Updated pelican.server not started error message.
Include the md / rst files in the dist