testutil: Add utility functions for testing

 - Print file name, line number, test name for debugging.
 - AssertEquals supports int,string, and bool. More on the way.
   Use reflections to test if their types match.
 - AssertTrue and AssertFalse works for boolean.
 - Print in red to highlight error message.
testutil: Add uint64 support

 - Replace existing if blocks with testutil.
Delete unused helper function in test_test.go