Prevent space between merged tags of the same type

[rob-3]

Fixes #35.

I was a little unsure about the change on line 365 - the tests pass with or without it, but it seemed right to also change it. Maybe you can shed some light on what that if does.

[matthiask]

Makes sense!

I think len(element) checks whether the tag contains subelements or something -- to be honest I don't remember the details. It appends the text of the next element either to the tail of the last subelement of itself or to its own text content.

[rob-3]

Great - thanks for the extremely fast response on this. Do you know when this change will land on PyPI?

[matthiask]

https://pypi.org/project/html-sanitizer/

Just now :)

Thank you!