Update dependency on nan to ~1.5.1.
Update dependency on nan to ~1.5.1.

Enables support for io.js at 1.0.1.

dieface/node-dtrace-provider,mgenereu/node-dtrace-provider,mgenereu/node-dtrace-provider,DataSweeper/node-dtrace-provider,mgenereu/node-dtrace-provider,dieface/node-dtrace-provider,mgenereu/node-dtrace-provider,dieface/node-dtrace-provider,DataSweeper/node-dtrace-provider,DataSweeper/node-dtrace-provider,dieface/node-dtrace-provider,DataSweeper/node-dtrace-provider