Add and re-export rgb crate for color handling

[alexeden]

Added

• #14 Add and re-export the rgb crate for all things related to color

Modified

• BREAKING #14 The NeopixelModule now has a Color associated type that must implement the ComponentSlice<u8> trait from the rgb crate
  • For convenience, any device that implements the NeopixelModule trait exports a type alias for its Color type, e.g. NeoKey1x4Color
  • The impl_device_module! macro has been updated accordingly when implementing the NeopixelModule for a device:
    • Before: NeopixelModule { num_leds: 4, pin: 3 }
    • After: NeopixelModule<color_type = NeoKey1x4Color> { num_leds: 4, pin: 3 }
• BREAKING #14 Functions that set handle colors in the NeopixelModule now take their Color associated type as parameters
  • Before: fn set_neopixel_color(&mut self, r: u8, g: u8, b: u8)
  • After: fn set_neopixel_color(&mut self, color: Self::Color)
  • Before: fn set_nth_neopixel_color(&mut self, n: usize, r: u8, g: u8, b: u8)
  • After: fn set_nth_neopixel_color(&mut self, n: usize, color: Self::Color)
  • Before: fn set_neopixel_colors(&mut self, colors: &[(u8, u8, u8); Self::N_LEDS as usize])
  • After: fn set_neopixel_colors(&mut self, colors: &[Self::Color; Self::N_LEDS])
• #14 All device examples have been updated to use the new NeopixelModule API
• #12 The register_write function on the Driver trait has been modified such that it no longer uses/needs const generics for buffer sizing (thanks @dsheets)