handle undefined href attribute
the html
the markdown
Merge pull request #6 from szepeviktor/patch-1

handle undefined href attribute
Fixes #5
Merge pull request #8 from szepeviktor/development

the tiny test
Don't install tests (but include them in PyPI package).

Fixes #9
Merge pull request #10 from mcepl/dont_install_tests

Don't install tests (but include them in PyPI package).
Fixes #9