Make a changelog for v3

[cshaa]

Version 3 brings a lot of changes, including breaking ones. Either a readme or a wiki page should include a complete changelog. Furthermore, make sure that each new feature is properly documented in the readme.

BREAKING DESIGN CHANGES:

• Fail early and reliably #22 (Returning runtime errors instead of undefined.)
• Add booleans #27 (Not converting booleans to numbers anymore.)
• Make modulo “mathematically correct” #36 (Modulo can no more return a negative result.)
• Remove random from standard functions to promote reliability #47

BREAKING BUG FIXES:

• Unary minus has precedence over exponentiation (ie. incorrect parsing of −x²) #41
• not in has weird precedence #42 (Changed not in to have the same precedence as in.)
• Exponentiation is left-associative #43 (Changed exponentiation to be right-associative.)

DEPRECATIONS:

• Change the ternary operator to if..then..else #34 (Ternary ? : operator deprecated in favor of if then else.)
• Change modulo from % to mod #48 (% deprecated in favor of mod.)

NEW FEATURES:

• Add operator “overloading” #30
• Make errors i18n-friendly #35
• Add chained comparisons #37
• Add constants #38
• Add option to use dot attribute access #44 (Optional chaining and dot accessor syntax.)
• customProp now has additional argument type: 'unescaped' | 'single-quoted'