filter out carriage returns for readfile

This is related to this pull request
https://github.com/yesodweb/shakespeare/pull/113 referrring to https://gist.github.com/gbwey/6833805

This change to readfile will filter out carriage returns as does Data.Text.IO.readFile.
Avoids the situation in windows where you read a file/then write it back and it is different.

Is there a reason why we don't just use Data.Text.IO.readFile?

Thanks,
Grant