Make more clear how tests find file to test

[chelseakomlo]

Hi,

It isn't totally clear in the readme how psychic resolves test dependencies. For example, if I'm testing a file resolver.c, and have written a test test_resolver.c, how are these dependencies resolved, when we are testing a function that is implemented in resolver.c and defined in resolver.h? Does the location of the test files matter? For example, we have a project that is divided into src/ and test/

Thanks :)
Chelsea