Add option to remove spaces from uploads filename

[bfrangi]

Hello, great work with this mdeditor package. I've been using this to write html emails for a django website and have recently run into this problem with sending images in the emails. After testing several possible causes, I've narrowed the problem down to the fact that my images, uploaded by mdeditor, have spaces in their filenames. I see that the image uploads are handled in the UploadView, and the filename is specified in this line of code. Would it be possible to add a configuration option to MDEDITOR_CONFIGS that enables removal of spaces (or replacement by some other characters) on upload? This would be very helpful, as right now this problem limits the functionality of the editor.

Happy to help with this if needed.

[pylixm]

这是来自QQ邮箱的假期自动回复邮件。您好，我最近正在休假中，无法亲自回复您的邮件。我将在假期结束后，尽快给您回复。