[FIX] remove_accents

[bosd]

Use an regex method to remove the combining diacritical marks

https://en.wikipedia.org/wiki/Combining_Diacritical_Marks

fixes #477

[bosd]

Some context:
To come up with this solution I tested a handfull of different methods to solve this.
Eventually I picked the one which did deliver the desired outcome and best performance.

I'm to humble to share the messy code of these tests. But here is the performance graph.

strip_accent function was clearly the slowest performing, when the input string increases.
So eventually I went for the one with the re one (shown in red).
The orange plot is the current implementation of remove accents. It's the fastest. But removes too much characters.
So not an option.

The purple plot is the same function as the red one. Only the python .re module has been exchanged for the regex module.

[rmilecki]

Quickly tested with my WIP tests coverage in #478, seems to work.

[bosd]

Should we hotfix this? by making another release on pypi.