Update Node.js addons documentation

v1.3.1

Bump NPM package version to 1.3.1

Use RTTI for classes identification

Replaced static variables for class types identification by std::type_index in order to resolve an issue with the classes identification across different shared libraries.

Removal of those static variables also leads up to better concurrency support with multiple V8 isolates (see #28)

Add module::set_const() for another module as a read-only property

According to nodejs/node#6216 only primitive values and V8 templates are allowed to set in a v8::ObjectTemplate.

v1.2.0

Bump npm package version to 1.2.0

v1.1.2

Set version 1.1.2

v1.1.0: Simplify class_singleton type registration

Use static class variable for the class type index, initialize it with number
of already registered classes. This approach prevents type indices duplication
in different DLLs on Windows, because pointer to `class_instances` is stored
in V8 data slot.

v1.0.0: Add package.json to make the project NPM compatible

To use v8pp for a native Node.js addon, add it as a dependency in
the `package.json` of the addon and pull in the path to v8pp in
the `binding.gyp` to use `#include <v8pp/class.hpp>` in the
addon .cpp files:

``` python
"include_dirs" : [
    "<!(node -e \"require('v8pp')\")"
]
```