Allow to generare quoted scalars if needed via providing a custom encode
options to Data.Yaml.encodeWith. So far two corner cases from yaml
itself (an empty scalar, and special strings) are omitted in the
implementation.
* Use lts-12
* Remove cache on fail and add workaround to fix build with stack
* Add dhall-lsp-server to lts-12
* Commenting out default stack.yaml
* Bump up megaparsec version
