Event flow re-factor
More re-factoring: changed sender from Dynamic to IFlxUIWidget in event functions where possible
Merge branch 'dev' of https://github.com/HaxeFlixel/flixel-ui into dev

Conflicts:
	flixel/addons/ui/FlxUIAssets.hx
Changing event signature so data and params are separate. "data" is always a primitive or object, "params" is always an array.
Refactoring so no uiEventCallback variables are needed, events now handled statically
Downgrading error to warn.
D'oh. Fixed stupid typo.
FlxUI compile fixes
Remove FlxUIInputText.forceCalcFrame()
Fixed RegExp glitch in FlxInputText and downgraded FlxUI warnings to notices
Merge branch 'dev' of https://github.com/HaxeFlixel/flixel-ui into dev

Conflicts:
	flixel/addons/ui/FlxUI.hx
Add .travis.yml
Add travis badge to the readme
Keyword order fixes
Fixed background rendering on FlxInputText for cpp/neko targets
Merge branch 'dev' of https://github.com/HaxeFlixel/flixel-ui into dev
Update README.md
Added ability to change FlxUIDropDownMenu contents after initialization, added "<line>" widget (documentation forthcoming)
Merge branch 'dev' of https://github.com/HaxeFlixel/flixel-ui into dev
Fixed FlxUIDropDownMenu to properly display added buttons/entries