Only render a null glyph once, instead of once per missing character.
Texture size, number of characters/glyphs refactored into enums/variables.
Strings (UTF-8) instead of const(char)[] (ASCII) in the API.
Minor doc fix.
Optional font texture size parameter for init.
Explanation of character count and font texture size.
Never use negative-sized scissor.

As the size of a scissor rectangle used in ScrollArea is defined as (width - something, height - something),
the rectangle would have negative size if e.g. the scissor area size is proportional to window size and the
window gets resized to a small size. This would result in a segfault (at least on AMD Catalyst/Linux).

E.g. when a user plays around with window width/height the program (even dimgui examples) would crash.

I worked around this by forcing the scissor area to be at least 1x1 pixels large.
Using const(char)[] instead of string in the API.
Very minor doc readability improvement.
Fixed a bug in imguiSlider.

`msg` contained an invalid UTF sequence since the entire `fmt`, not just
the result of formatting digits, was formatted into `msg`.
The demo example now shows a use of Unicode characters.
Merge pull request #2 from kiith-sa/unicode-support

Unicode support
Merge pull request #3 from kiith-sa/patch-1

Never use negative-sized scissor.
constness fix for D 2.066
Merge pull request #5 from Munrek/master

constness fix for D 2.066