Remove Map.prototype.{filter, map}
Update README.md
Move Array.prototype.includes to stage 2

Previously known as Array.prototype.contains
Update Array.prototype.includes URL

Now under tc39
Merge pull request #16 from jhusain/patch-1

Update README.md
Add `trailing commas in func exprs` as a stage 1 current proposal

Per the meeting notes from the Sep'14 meeting, this proposal is
currently at Stage 1.

https://github.com/tc39/tc39-notes/blob/master/es6/2014-09/sept-24.md#51-trailing-commas-in-function-call-expressions-and-declarations