raspberrypi-ua-netinst v2.4.0 RC1

RC1 notice:
Report customization bugs in #171 or #172.

Thanks for all your support and feedback!

Known bugs:

• installation via WiFi not working
• incompatible with wheezy

Changelog:

• support for version 4 model B
• support for Debian 10 (buster)
• added or changed configuration variables:
  • release is set to "buster" by default