By not calling validate(), we can add
non-invasive features which will be simply ignored when user-code
is compiled against an old version. That way, we can often
avoid a minor version-bump.

The user can call validate() himself if he prefers that behavior.

Fixes #88 and #56.

This is an improper solution. If multiple Readers exist,
then the effect stackLimit is reduced because of side-effects.
But our options are limited. We need to address the security
hole without breaking binary-compatibility.

However, this is not likely to cause any practical problems because:

* Anyone using `operator>>(istream, Json::Value)` will be using the
new code already
* Multiple Readers are uncommon.
* The stackLimit is quite high.
* Deeply nested JSON probably would have hit the system limits anyway.

And throw instead of return null for invalid settings.

Remove some experimental classes that are not needed for 1.4.0. This also helps 0.8.0 binary compatibility with 0.6.0-rc2.

Reimplement the new Builders.

Issue #131.

We use Json::Value to configure the builders so we can maintain
binary-compatibility easily.

Deprecate the new Builders.

see issue #131

CharReader/Builder

I guess we should but the patch-level version. We will set the version properly soon...