Run rubocop on stdlib

Fixed nodejs/irb indentation.
Fixed new stuff from master.
Disabled Style/InfiniteLoop cop.

- remove b flag silently (this already matches how Node reads files)
- detect the encoding opti...

Fixes https://github.com/opal/opal/pull/1776#issuecomment-371802175

Fix xstring management

- extract to a separate file
- avoid fancy stuff when the x-str is passed to Compiler#returns, j...

Add Date#to_n (in native.rb)

This option will command how the builder should behave when a required
file is missing. Previo...

codeclimate rubocop

"*/check-ci" is used for quick checks before pushing direclty to master

Just a reminder on how it works and where to look.

Just for libs requiring it, not intended as reliable.

Helpers should be added in the future for useful stuff (e.g. #compile).

* Optimize String#unpack

Do not use chunk/buffer for the following pattern:
- 'C*'
- 'c*'
...

Add rubocop

Therefore opal-compiler.js needs to require 'corelib/string/unpack'

https://github.com/whiteq...