Minor corrections to main and Q&A pages
In the main page, section **Input**,  the old parameter `period` is mentioned three times, although the correct now is `btnp(key, [hold], [repeat])`.

I had to look at the source when upgrading my old 1.5 code.

This change should be also noted in the Q&A page, section **How to Migrate to a New Version**, along with the removal of the `pal` parameter from `init()`.

Thank you very much for such nice environment!