unit tests

[eastein]

https://github.com/joewalnes/tinytest/ may be a nice framework to try out. Exercise the DNS code in particular.

[eastein]

Framework added! I kind of want to be able to run the unittests on the ESP, though... I should plug into tinytest to redefine how printing out works, to send over the uart instead, and make an ESP RTOS system for running the tests (a user_init and the RTOS imports).