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

Test cases succeed as expected, but the example in #367 is not fully
realized yet.

An optional parameter for dump() allows to set the character to use for
indentation (default: space). In case a JSON value is serialized to an
output stream, its fill character is used (and can be set with
std::setfill).

I forgot to consider the offset.

a simple acceptor function

needed for VS2015.3 with /std:c++latest

These classes are now constructed with an interface adapter. This moves
complexity from various places into the interface adapter class, or to
some factories which now implement the different flavors of input.

Furthermore, input adapters are kept in std::shared_ptr to avoid the
need of manual deletion.

This implementation forwards the iterators to std::map::insert.

We totally forgot to implement the comparison operators other than ==
and != for scalar types. Consequently, comparing a JSON value with a
scalar type led to compile errors.

Do not store eof() in a char buffer…