Move converters to namespace

[B3zaleel]

No description provided.

[Happypig375]

Are you sure this is backwards-compatible?

[B3zaleel]

The main code hasn't changed, just the namespace. In case we need to add converters for other mathematical writing formats, it might pollute the main directory.

[ForNeVeR]

@B3zaleel yes, it is a breaking change. In case any library user uses the converter in the current namespace, their code will break with library update.

Although, technically, we could still make breaking changes (because we're still in 0.x version range), and I welcome everybody to share their thoughts on the matter. It's better to break things right now, before we've entered the 1.0 version range.

I was going to deny that breaking change, but @B3zaleel made a really good argument about possibility of adding new converters.

[ForNeVeR]

Thanks for your contribution!