make constructor initializer less lines
remove redundent empty line
move 'typedef unsigned long long = seq_t' from cargseq to cbit. and replace unsigned long long in cbit to seq_t
add a failure test for cbitstr. new function bits_from_string is that transform str "0101" to actual value in compile time.
pass the test of cbitstr
use invalid argument instead runtime error
observe that use function template specializing in constexpr leads compile error