remove superfluous check

Improvement of PR #3053

allow Container.addChildAt when zero children

_parentID was not in the class. Hidden class problem

fix for #3027

updated some doc comments (#3038)

addChildAt index ...

Index can be 0

clean up to be specific

Huge refactor to match a new shiny eslint file.

Fix linting issues

merge #2956

fix issues w/ Container destroy; see #2863 and #2995

Prefer const (#3002) ...

* added prefer-const rule to .eslintrc

* eslint const autofixes

* manual let to const changes; lint free;

* added brace style 'allman' to eslintrc

* brace style, comment fixes and default arg

* brace style fixes

* more brace styles

* Point default args

* Point brace styles

* Observable Point default args

* more brace styles

* jsdoc comment style

* brace style

* brace styles and small jsdoc fix

* brace styles

* removed unneeded eslint inline comment

* brace styles; lint free

bounds and transform for invisible containers.

some more es6 changes (#2969) ...

* some more es6 changes
- const instead of let if possible
- arrow functions
- string templates
- argument defaults

* object property shorthand

* some more es6 changes
- const instead of let if possible
- arrow functions
- string templates
- argument defaults

* Revert "Merge branch 'dev-es6-sb' of github.com:stbaer/pixi.js into dev-es6-sb"

This reverts commit 8d3af81, reversing
changes made to e8b9948.

* Revert "Merge branch 'dev-es6' into dev-es6-sb"

This reverts commit 3eeaf79, reversing
changes made to fb69536.

* Revert "Revert "Merge branch 'dev-es6-sb' of github.com:stbaer/pixi.js into dev-es6-sb""

This reverts commit c860228.

* fix RenderTexture, incomplete merge

* fix for text font properties

* reverted some changes

* checked out License, Readme and Contributinf from dev-es6

* editorconfig updated: 2 spaces for .eslintrc

* added eslint rule: spaces around fat arrow

* used eslint fix for consistent spaces around fat arrow

* don't allow scale.x or scale.y to be 0 in displayObject setTransform

* removed jshint comments (again)

removed old jshint comments; replaced jshint in CONTRIBUTING.md with eslint

Replaces jshint with eslint, using babel in loose mode

Update imports and exports, getters and setters

Disallow the use of `var`

Implementing classes using the new ES6 syntax (#2936) ...

* Migration to ES6 classes

* Migration to ES6 classes

* Migration to ES6 classes

* Migration to ES6 classes

* Using babelify to transpile ES6 code

* Adding babel-preset-es2015 in devDependencies

Fix process interactive (#2855) ...

* Added 1 extra check in the procesInteractive to check if children exists before attempting to call children.length
this would've thrown an error if you remove stuff in an onMouseClick for example.

* smaller diff maybe

* changed remark

* Better and faster fix
set interactive and interactiveChildren to false on the DisplayObject.destroy()
this way no extra check is needed in the processInteractive function.

sprite bounds tweaks (#2817) ...

* sprite bounds tweaks

* added a trimmed sprite test

* tweaks to tint

wrong place i know..

dots and commas (#2818)

Destroying a DisplayObject will remove itself (#2809) ...

* Destroying a DisplayObject will remove itself

* Container removes children before destroying

* Fixed destroy order

* Removes extra whitespace

* Updates with Ivan's suggestion for Container destroy

* Removes listeners when destroying

* More verbose destroy comments

* Typo

forgot a filter check :/

fixed little issue with _enabledFilters being null

added enabled to filters (#2798) ...

* added enabled to filters

* lint that code!

fixes for cacheAsBitmap

initialize _localID (#2789)

fix call to getBounds (#2788)