Rewrite code with the NAN interface

[mengxumx]

In the migration from Node.js v0.12.x to Node.js v4.x, the Node.js C++ addon interface has changed a lot. So I rewrote the DB2 connector using the new interface. Once again, in the new version Node.js v8, the C++ interface has changed again. To resolve the problem, we need to rewrite the code with the NAN interface.

https://github.com/nodejs/nan

[mengxumx]

Duplicate of #15.