Refactor all widgets to HtmlElementView

[krokyze]

This pull request:

• Migrates all widgets to HtmlElementView so now scrolling, updating absolute positions, adding, removing html elements is automatically handled and there's no need of RenderScrollListener or RouteObserver.
• Adds TextRendererStyle to fix #10
• Moves _regExp.hasMatch to root RobotDetector so it isn't called every single time *Renderer widget builds
• Adds debug option so robot mode can be easily enabled
• Adds optional text for TextRenderer
• Changes src to optional for ImageRenderer

[iamSahdeep]

v0.5.0 published, Thanks again @krokyze