Support for absolute paths

[nicky1038]

@radarsu Hello, thank you for sharing this library! I was very happy when I found out that it exists, after some unsuccessful tries of setting up ts-node in my code.

Still, there is a huge limitation: this library allows working only with relative imports. However, in code, we could get tsPath in several different ways, based on what the provided path is.

Do you mind if we make this change? I could make a PR, this seems not to be hard.