Use Text instead of String in parser

[poscat0x04]

String is not fast nor memory efficient, Text is better in almost every case.

[tdammers]

The reason for this is because when I started developing Ginger, Parsec didn't accept Text as its input yet. I agree that Text would be the correct choice here, and I have a patch ready in the string-to-text branch, but I'm mildly undecided about how to handle the resulting breaking change. Options:

• Just apply the patch as is, introducing a hard breaking change (i.e., users will have to change their code to use Text instead of String as well)
• Rename the Text-based API, and provide a compatibility shim for String
• Perform some typeclass voodoo to make the parser support both

I'll give this some more thought, any input on the matter is welcome.

[mulderr]

Personally, I'm +1 on hard breakage, forgetting String altogether and a major version bump with a clear note in the changelog.