Fix bug in input.lua, make 0.9-ready, add utf8 editing

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.

README.md

@@ -135,7 +135,16 @@ Quickie is an [immediate mode gui][IMGUI] library for [LÖVE][LOVE]. Initial
 	end
 
 	function love.keypressed(key, code)
-		gui.keyboard.pressed(key, code)
+		gui.keyboard.pressed(key)
+		-- LÖVE 0.8: see if this code can be converted in a character
+		if pcall(string.char, code) code > 0 then
+			gui.keyboard.textinput(string.char(code))
+		end
+	end
+
+	-- LÖVE 0.9
+	function love.textinput(str)
+		gui.keyboard.textinput(str)
 	end
 
 # Documentation