Ruby STL container ranges and slices fixes.

Access via ranges and slices now behave identically to Ruby arrays.
The fixes are mostly for out of range indices and lengths.
- Zero length slice requests return an empty container instead of nil.
- Slices which request a length greater than the size of the container
  no longer chop off the last element.
- Ranges which used to return nil now return an empty array when the
  the start element is a valid index.

Lib/ruby/std_array.i

@@ -41,7 +41,7 @@
     getslice(const std::array<T, N>* self, Difference i, Difference j) {
       using Sequence = std::array<T, N>;
       typename Sequence::size_type size = self->size();
-      typename Sequence::size_type ii = swig::check_index(i, size);
+      typename Sequence::size_type ii = (i == size && j == size) ? i : swig::check_index(i, size);
       typename Sequence::size_type jj = swig::slice_index(j, size);
 
       if (ii == 0 && jj == size) {