Add oneOfStrings
Add many1Till

This seems like a useful combinator to add to the core library, which
rounds out the existing combinators `many`, `many1`, and `manyTill`.
Add line and column information to positions for better error messages.
Merge pull request #12 from greghendershott/oneOfStrings

Add oneOfStrings
Merge pull request #13 from greghendershott/many1Till

Add many1Till
Merge pull request #14 from greghendershott/line-col-pos

Add line and column information to positions for better error messages.
scrbl typos, add manyTill tests
update json parser example with ln and col

- not sure how to update line