Merge pull request #83 from emoon/master

Fixed Clang warnings
Using sqrtf, cosf, sinf. Made STB_TEXTEDIT_ implemtations static. Tweaks.
More fixes for ultra pedantic Clang -Weverything
Fixed comment
Fixed compatibility with std::vector if user decide to #define ImVector
General fixes of Columns() api. User has more flexibility in the way to fill cells.
Style editor: colors list inside a scrolling region
ShowTestWindow: fixed example app from not displaying when header is collaposed.
Added "performance" screenshot
Added "performance" screenshot
Update README.md about performance
Fixed Tab > space
PushStyleColor/PushStyleVar can be used outside the scope of a window. Added 'count' parameter to PopStyleColor/PopStyleVar
MouseWheel input is normalized
Update README.md
Version number
PopStyleVar() fix. OOPS
Added ImGuiWindowFlags_AlwaysAutoResize + example app. Calling SetWindowSize(0,0) force an autofit without zero-sizing first.
Not word-wrapping on apostrophes
InputText support for completion/history/custom callback + added fancy completion example in the console demo app

Unfortunately quite messy because of the UTF-8 <> wchar confusion going
around. Not well tested for UTF-8 compliance with non-Ascii characters.