type of iterator of lhs and rhs may be different
do not allow any conversion in element type
check a value type of iterators
add explicit default rvalue ctor and assign operator
tiny cosmetic fix
check the length of C array

zero-length array is not permitted in ISO C++.
add test for zero-length array_view
add ctor for std::initializer_list
make_view() and is_array_class<> for std::initializer_list
rename test file
fix make_view(Iterator, Iterator)

make_view(Iteraotr, Iterator) ctor is explicit
add more tests for operator == for initializer_list
add test for make_view()
use explicit construction for slice() member functions
test for non-safe slice() member functions
do not access a front element of array_view if it is empty.
add test for operator<<
add a newline before output of test