Inherit release script's stdout

[kettanaito]

There may be continuous stdout coming from the release script:

{
  "prerelease": "npm test",
  "release": "release publish"
}

Current behavior

The stdout is not streamed but is instead printed as a single chunk once the release script exits.

Expected behavior

Stream (inherit) the stdout of the release script so developers can observe the execution of the command, and any underlying commands, in real-time. As a side-effect, I think this will also improve the error handling, as the stderr will also be printed out as it comes in.

[kettanaito]

This is implemented in #32.

[kettanaito]

And then fixed to be an actual stream in #57 and #61