fixing wrong filename written to md5 hash file

[ccoenen]

Currently, when md5 files are being written, they contain

9e777f886ce454ddc32c6ff3f3d99908 *startrek_thenextgeneration_thespacebetween.epub.md5

but this is wrong. The filename that's being referenced does not END in .md5. Only the hash file does. The correct naming would be:

9e777f886ce454ddc32c6ff3f3d99908 *startrek_thenextgeneration_thespacebetween.epub

This PR fixes it.

[ccoenen]

I just realized that this includes commits I did not intend to include. Sorry!

[MayeulC]

Do you want me to cherry-pick 0135dd2 ?

I can investigate the issue, unfortunately, I've been short on free time recently (alas, #20 has been sitting on the top of my priority list for some time...).

[ccoenen]

This is one of two Pull Requests that were merged into talonius' version of hb-downloader (see https://github.com/talonius/hb-downloader/pull/13 and https://github.com/talonius/hb-downloader/pull/14) I also proposed (and have finished) single product download, see https://github.com/talonius/hb-downloader/issues/12 for details.

I was not sure which of the two repositories is more active. I'm sorry for cross-posting to both, that was probably more work for everyone involved. Feel free to cherry-pick any of the thing that you like!