Changing the way of using Python function into UltiSnips.
I have search a way to have acess to a function in many snippets file without copying it.
Because I think It was messy to add them into snippets files, I have create a new directory called python.
After I want to be able to import them. But for be able to import them without import manualy into each files with `sys.path.append('directory')`, I have add the directory to the runtimepath.