Same as get_ptr() but for references.
If the type is incompatible it throws (get_ptr() returns null).
Implemented in terms of get_ptr().

The intention of the current code is to detect a pointer-to-const but instead it is detecting a const-pointer. See #134

STL iterators used by json::iterator don't pass this test in Debug mode.
The test does pass in Release mode, so I felt the best thing to do was selectively disable that test.

It doesn't really make sense to stream an iterator.
Besides, this was causing trouble in MSVC in Debug mode (see #125)

exception-safe object creation, fixes #118

Overload parse() to accept an rvalue reference

Use the right variable name in doc string

Fix small oversight.

Remove superfluous inefficiency

fixed typos in comments for examples

try to avoid MSVC bug (https://connect.microsoft.com/VisualStudio/feedback/details/797682/c-decltype-of-class-member-access-incompletely-implemented)