Use bytes instead of strings, ditch fancy_regex for regex crate

[SkeletalDemise]

Currently lemmeknow uses the fancy_regex crate for matching regex. The problem is that it doesn't support bytes. The regex crate, however does: https://docs.rs/regex/1.0.0/regex/bytes/index.html

If there is no reason to use fancy_regex then we should switch. Both pyWhat and lemmeknow only support ASCII strings. We need to support UTF-8, UTF-16, etc. and bytes.

See this equivalent pyWhat issue: bee-san/pyWhat#34

[swanandx]

regex crate does not support look-around, so if we try to use it, we are not able to compile the regular expressions from regexs.json file.

That is why we use fancy-regex.

lemmeknow do support UTF-8 as the Strings are UTF-8 in Rust. ( and we also tested with UTF-16 right? ).