Merge pull request #10 from MLXXXp/widget_val_range

Handle full signed 16 bit ranges for widgets.
Merge pull request #11 from MLXXXp/slider_ticks

Simplify slider widget drawFace() function.
Merge branch 'master' of https://github.com/geekammo/MicroView-Arduino-Library
Add uView.scrollLeft() function.
Same as existing uView.scrollRight() but in the opposite direction.