Add base munit structure for coverage and unit tests.
- Wont work without currently without workarounds to core default.png asset in FlxSprite and null calls to stage.
Use embed for resolving default FlxSprite image in munit tests.
Replace stage references with Lib.current.stage to avoid munit null errors on stage.
Dispatch events in test for ENTER_FRAME.
Add test to travis.
Merge remote-tracking branch 'origin/dev' into unit-test

* origin/dev: (98 commits)
  Some more compile fixes for flixel-conditionals
  Compile fixes
  Fixed a typo, should be elasticInOut, not elasticInOunt.
  FlxGamepad: Initialize dpad vars to prevent neko crash
  Replace UInt by Int
  SoundTray / FocusLostScreen: Don't take camera zoom into account, fixes HaxeFlixel/flixel-demos#69
  dont use the same inthelper twice in the same function
  Added elastic easing functions.
  Update CHANGELOG.md
  FlxMouse: Hide flixel cursor on focus lost (makes #762 less noticable), fix bug where cursor disappears after regaining focus
  FlxRect: Allow to set left / right / top / bottom
  these values are better for mouse
  FlxBasic.draw() optimization (thanks @steverichey)
  FlxTween: Add option to delay tweens, closes #784
  FlxMouse: Compile fix for bf91873da88c0f1b17ffed9d33725f34b2944197
  added couple checks for native cursor
  scale and offset for native mouse cursor
  CHANGELOG: More readable format, update
  Add FlxSprite.getGraphicMidpoint(), add convenient default values to FlxSpriteUtil.drawCircle()
  Revert "flixel.system.resolution -> flixel.util.resolution"
  ...

Conflicts:
	flixel/FlxGame.hx
Remove null references to stage for munit tests.
test travis
testing travis
Use mcover on base flixel package
Add flixel-addons dev to coverage test.
Exposing `FlxTween.backward`
Increment dev branch version
FlxGamepad minor cleanup
Fix function keyword order in some places
Another keyword order fix
Making `backward` read-only.
Merge branch 'dev' of https://github.com/HaxeFlixel/flixel into dev

Conflicts:
	flixel/tweens/FlxTween.hx
Removing unnecessary backward set
Remove depreciated _ease variable. Caught by api doc generator.
Add PixelPerfectScaleMode

Added PixelPerfectScaleMode, a scale mode which scales up the game to
the highest integer factor it can, maintains the aspect ratio, and
windowboxes the game if necessary.