Fixed potential memory leak in sf::Font
Added documentation note on coordinates and undistorted rendering
Added String::replace() methods

Based on pull request #355 from abodelot
Updated copyright year to 2014
Fixed typo in Windows keyboard implementation

Fixes #516
Added String::substring() method

Based on pull request #355 from abodelot
Merge pull request #509 from ophui-/master

Fixed potential memory leak in sf::Font
Fixed forgotten members in sf::Font::operator=
Removed unnecessary null pointer checks in Window.cpp

Fixes #532
Avoided unnecessary toLower string conversions
Merge remote-tracking branch 'Laurent/master'