Editorial tweaks + how to print a given element of a dictionary

Just a bunch of editorial tweaks really. I've also added an example how to print a given element of a dictionary.
Well, actually boolean comes from the surname of  George Boole who came up with something that is now called Boolean logic. So formally, it should be capitalized. I quess, it's one of these words that were written in a capital lettler first (like Internet, Web, etc), but now they tend to be written in lower case. Wikipedia uses capital letter for Boolean, but I don't mind to change that. Just, It wasn't consistent before anyway.