Add pair support, fix CompatibleObject conversions (fixes #600)

Instead of calling CompatibleObjectType iterator-range constructor,
first convert json::value_type to CompatibleObjectType::value_type

#550 Fix iterator related compiling issues for Intel icc

This reverts commit c4ab8f82.

I totally forgot about byte order marks in this scenario.

Change the definition of the operator override of reverse iterator to using the result of the base class directly

operator>> now works as expected.

Fixed to make sure no token is "overlooked".

Also added a Travis builder with -std=c++1z

fix doxygen error of basic_json::get()