Adding missing requirement 'shapely'.

[sepastian]

See #9.

[poke1024]

@sepastian I'm a bit hesitant to merge this, as shapely is in https://github.com/poke1024/origami/blob/master/requirements/conda.txt. This might be more of an documentation issue.

The current idea here is that packages that exist in conda are in https://github.com/poke1024/origami/blob/master/requirements/conda.txt whereas the rest lives in https://github.com/poke1024/origami/blob/master/requirements/pip.txt. Did you manage to install a working installation solely via pip? If yes, maybe I should get rid of conda altogether and only supply one requirements.txt.

[sepastian]

Thanks for the clarification @poke1024. I will try installing using only pip and keep you updated.