1) [input.lua] Pressing backspace while the cursor was at the beggining
of the text removed the first character. Fixed thanks to riidom.
2) [LÖVE 0.9] Use setLine(Width|Style) instead of setLine. Split
keyboard.pressed() into keyboard.pressed() and keyboard.textinput().
(see readme)
3) [utf8.lua] Add support for UTF-8 text editing. May still fail
spectacurlarly with invalid UTF-8 strings.
Changes to default-style.lua:
Prevent text from being drawn past bounding box via love.graphics.setScissor().
The cursor and surrounding text are kept in visible range by calculating a draw offset.
Made a marginally simpler & more readable Slider draw routine using rectangles instead of lines.
Also the ends of the slider "track" are capped now. I split this commit in case a rollback is desired.
Slider, when vertical, was drawing the grab box with inverted position. Center "track" had incorrect orientation.
Also, slider.lua was passing a bunk table to group.getRect().
