Grammar, Spelling, and a small clarification

A few spelling and grammar fixes.
I added "Tox ID" in some places where only "ID" was used to reduce confusion with other IDs, i.e. DNS discovery ID.

I rewrote the paragraph on reading the DNS TXT records if there are more than one returned by the lookup. I thought it was a bit ambiguous on which record to read if there are multiple records of the same version, as the standard states the clients are *free* to choose the first one. They *should* use the first one.