Remove `Text.Parsing` module prefix

[thomashoneyman]

To go along with purescript-contrib/purescript-parsing#147 -- this library could just as well do with just using StringParser as the module prefix, rather than including Text.Parsing, as we don't follow the Haskell example of putting all text-related packages under a Text grouping.

[chtenb]

While we're at it we might as well update the module structure a bit. Since this is a very simple package I think it would make sense to have a single module act as the main API, reexporting from Combinators and CodePoints, similarly to purescript-strings (see https://github.com/purescript/purescript-strings/blob/master/src/Data/String.purs)

[chtenb]

@thomashoneyman What is the attitude towards these kind of changes in the PureScript ecosystem? Should we just do this the next time we push a breaking change? This would be the next release.

[thomashoneyman]

@chtenb Core libraries avoid breaking changes, and so do particularly widely used contrib libraries (Aff, Argonaut), but otherwise it’s up to the maintainers to decide when a change is worth breaking things.

When breaking things we generally try to make sure the upgrade path is well-described. This change is a simple find-replace so that’s easy — unless another package in the package set is using the same module names. Shuffling the modules around is a bigger change, so I hope we can still make it easy to migrate. I suppose that would just be changing all your imports to one single import though, so that’s easy enough.

[chtenb]

Is there a particular reason we don't use the Text namespace anymore by the way? Or put another way, do we have a formal set of guidelines about module names somewhere?