V2.5.5: new release to upgrade to CSFML 2.5.2 (API changes)

Changed

• The required version of CSFML has been upgraded to 2.5.2. This implies changes in the API and incompatibility to any previous CSFML release. #21

Fixed

• Many improvements and fixes to make the API documentation more readable and faithful to the original.
• Added named numbers in Sf.Window.Joystick as in original (anon enum was ignored) f0f70e6

Full Changelog: v2.5.4...v2.5.5