Update documentation to HAL Explorer

[toedter]

While the HAL Browser module was removed and replaced by HAL Explorer, both the readme of this project and the Spring Data REST reference documentation still refer to the HAL Browser. Please update the doc to refer to HAL Explorer.

If it would help, I could contribute to that.

[mp911de]

Good catch. Feel free to submit a pull request to speed things up.

[toedter]

I have created a pull request.