Add urls support to collections.

[FledgeXu]

Fix #59

[rgaudin]

Good!
Can you please:

• Add a check for clashing filenames? If we request (directly or indirectly) several files to be stored at the same path, the first one will get the spot and the rest will silently point to it. We should raise on such conflict.
• Update the README to mention the new format(s)
• Update the CHANGELOG to add the feature.

[rgaudin]

Great but duplicate name is not working

[
    {
        "title": "Fledge PDF",
        "description": "Someting in his ZIP",
        "authors": "n/a",
        "files": ["test.pdf"]
    },
    {
        "title": "Tarifs I SAGO",
        "description": "Tarifs électricité Mali",
        "authors": "EDM",
        "files": [
            {
                "archive_member": "test.pdf",
                "url": "https://isago.rskg.org/static/tarifs-isago.pdf",
                "filename": "test.pdf"
            }
        ]
    }
]

This doesn't raise while it should.

The problem is you are looking for duplicates in path instead of filename. path is used only to retrieve member_name (maybe it should be renamed) and we don't care about using it multiple times.

[FledgeXu]

The problem is you are looking for duplicates in path instead of filename. path is used only to retrieve member_name (maybe it should be renamed) and we don't care about using it multiple times.

I see. you are right, filename is the name of the last file that will be put into zim.

[rgaudin]

You may also want to only display duplicate ones (using a set) ; otherwise

ValueError: Files in collection are duplicate:
 - test.pdf
 - test.pdf

You should also look into refactoring a bit test_collection to please Codefactor

[FledgeXu]

maybe it should be renamed

I just changed the path to the uri. I think it's more appropriate.