TOML Support in dhall-haskell

<p>This is a proposal to add serialization and deserialization support for TOML in the functional configuration language Dhall. TOML is a relatively new configuration language that is easily human readable, supports dates and times, and is unambiguous. The biggest users of TOML are Rust’s Cargo, and consequently many Rust programs read TOML. Adding support for TOML in Dhall would mean users do not have to choose between readability and the power to program their configurations.</p>