This adds the vimwiki_local `html_filename_parameterization` option (0|1)
which performs the same sanitization of filenames as does the
vimwiki_markdown gem.
For example, if your file is called "My File.md" it will be written out
as "my-file.html".
If the html_filename_parameterization options is enabled, we also _do
not delete_ non-matching html files when the VimwikiAllToHtml command is
run.
Closes#129
5f01182468