More integer information
Removed Number.toInteger() as it's not in the spec
Complete chapter 1, address bugs (fixes #51)
Add chapters 2 and 3 to the book
Some chapter 2 cleanup
Fix description of early access of let variables (fixes #52)
Mention Number.parseInt() and Number.parseFloat()
Remove chapter 3 from book pending syntax fixes
Revert "Fix description of early access of let variables (fixes #52)"

This reverts commit 852dd7f63d051eee83257fc88251d2a8e5ee912c.
Merge branch 'master' of github.com:nzakas/understandinges6
Type safety with proxies
Fix table layout for Math methods
Add section on spread operator, polish section on arrow functions a bit
Added note to chapter 2 about default params (fixes #57)
Add mention of typeof when used with let declarations (fixes #49)
Added intro to Chapter 2 and revamped default params section
Finish up chapter 2
Fixed example consistency in Chapter 2
Clarify that shorthand methods are anonymous (fixes #44)
Added .name property for functions and empty arrow functions to chapter 2