Suggested updates for paragraph on builtins

- Don't worry...would flow better with a comma instead of a period and an exclamation mark to exclaim just how easy it is! (just a suggestion)
- ', below,' would indicate that below is the builtin types being referred to, so removed the commas for sake of clarity
- 'in Go' before 'unlike the C way' sets up the difference with the emphasis on Go rather than the emphasis on C, which should make for a nicer contrast. (just a suggestion)