Handle wrapping, add hideCursor option

[novemberborn]

Count how many rows are taken up by the spinner and the text and clear the appropriate number of lines. Fix clear() so it doesn't clear further lines until render() is called again.

Fixes #38. Fixes #7.

Add hideCursor option. Fixes #27. Users may still hide the cursor outside of Ora.

There aren't any tests for hiding the cursor so I didn't add one for not hiding it either.

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I did a quick test in the Windows command prompt and the wrap handling seemed to work fine.

[novemberborn]

FYI I'm integrating this with AVA just to make sure it all works as expected. No need to merge just yet.

[novemberborn]

OK this seems to work well now. @sindresorhus et al please let me know if anything needs changing.

[sindresorhus]

This looks good :)