0.5.0

Added

• Config - A class for handling a configuration.
• ConfigOption - A class for handling config options.
• create_options(options) - Creates config options from a list of descriptors.
• passthrough(value) - A passthrough mapper. It returns the value as it is.
• boolean(value) - Converts a value to a boolean value.

What's Changed

• Feature/Config classes by @jsconan in #16
• Release 0.5.0 by @jsconan in #17

Full Changelog: 0.4.0...0.5.0