a simple acceptor function

Default arguments are forbidden in lambdas.

Creates all well-formed sequences of bytes up to length 4. Furthermore,
creates ill-formed sequences by removing required trailing bytes or
changing bytes. As the tests can take a lot of time, preprocessor
symbols are introduced.

As I learned in https://github.com/melpon/wandbox/issues/209, this
library is already installed at Wandbox, so we need to adjust the
examples to use `#include "json.hpp"` insteas of `#include <json.hpp>`.

std::setw needs the iomanip header (at least with GCC).

The example with the size() operator is bad: using operator[] already
changes the size of the object. The fix makes it clearer.

These files were never meant to be versioned.

Taken from
https://github.com/travis-ci/docs-travis-ci-com/pull/746/files.

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.

To test a fix for issue #464 (not yet implemented), we first need to
have  an MSVC build with “/permissive- /std:c++latest /utf-8”.

One test case for CBOR and MessagePack assumed little endianess.

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…