Column number support

[joshprice]

This is currently needed for precise error messages in both https://github.com/graphql-elixir/graphql and https://github.com/absinthe-graphql/absinthe.

[joagre]

I also miss column number support.

[rvirding]

Hmm, is the first character in a line in column 0 or 1? And do you treat tabs as one character or "pad" them out to the next 8th position? Just thinking out loud really.

[MarkoMin]

Don't know if it is still relevant, but I've implemented column number support as this year's Spawnfest project.
Started counting columns at 1 and I've set the default tab size to 8, but left the possibility to configure it to your needs.
The project can be found here. Any feedback is very welcome :D