Minor typos in Ch02

[rdeits]

I just started looking at the ThinkJulia book. It looks really nice--thanks for putting this together!

Just a couple things I noticed:

• In the second paragraph of https://benlauwens.github.io/ThinkJulia.jl/latest/chap02.html#Variable-names-1 "variables names" should be "variable names".
• In the code block below, there should be an error message after more@ = 100000 but instead type = "Advanced Theoretical Zymurgy" is written twice.

[BenLauwens]

Thanks!