Added Vertical Slider styles to Slider widget

Added WIDGETSTYLE2 (like 0, but vertical) and WIDGETSTYLE3 (like 1, but
vertical). NOTE: I don't have a build environment, so I can't even
promise this will compile! So if it's crap, just treat it as a concept
for an enhancement request!
Fixed my typo in MicroView.cpp

Fixed my typo in MicroView.cpp
Many bugs fixed

OK, this version is actually worth looking at. Previous had more bugs
than you could shake a stick at.

vert_slider_test.ino illustrates the two slider styles, vertical
versions of the two existing styles
Merge branch 'vertical-slider' of https://github.com/czetie/MicroView-Arduino-Library into czetie-vertical-slider
moved example to example folder
added Vertical Slider example
Merge branch 'czetie-vertical-slider'
merged czetie vertical slider