Fix typos

[amuricys]

Caught them in the preface and first chapter, some in the later chapters were the result of searching (e.g. eachother)

[eRedekopp]

A couple more that I noticed:

Chapter 1 line 258/9:
"""
We imagine that the clock is going about its business inside the box, and that is [it] shows the hour it is currently displaying on the outgoing wire.
"""

Line 700:
"""
We say that a deterministic system $\Sys{S}$ as [has] ``no inputs''
"""

[eRedekopp]

On an unrelated note, I'm not sure I've ever seen that "down arrow" notation in Definition 1.3.3.9 before and it kinda caught me off guard while reading. It might be worthwhile to spend a sentence or two explaining it.