add asserts printing custom message on fail
remove tester tests
upgrade and fix tester

* Add `_tester->fail = true` lines that were missing.
* Write FAIL() macro
* print_test_summary now displays summary in one line
fix tests

* Print the value of 'pos' in 'mkmodule_pos'.
* Disable segfaulting 'kmparticle_id_unknown_returns_nonzero' test.
sys unittest

See #6
add new tests to main checker

See #6
rename test_main.c to main.c, again