CONTRIBUTING.md: update contribution guidelines
if-else: reformat, so it's easier to see that this is an assignment
box: use new box and Box<T> syntax, clarify that box is a smart pointer
literals: show usage of underscores
Merge pull request #58 from kud1ing/patch-4

if-else: reformat, so it's easier to see that this is an assignment
tuples: show how to create one element tuples. Closes #59
box: wrap lines to 75 chars
type: wrap line to 75 chars
generics: remove claim about usage. Closes #56
add new chapter on RAII
move: rewrite chapter on Ownership. Closes #46
borrow: more in-depth chapter on Borrowing
lifetime: rewrite chapter on Lifetimes. Closes #24
reorder some chapters
array: reword chapter, show runtime failure
clone: focus on the Clone trait
constants: more details on the 'static lifetime and &'static str
iter: reduce length of the example output
vec: make clear that pop, returns the removed element
clone: rename chapter