Adjust CMake module to provide correct deps on OSX

Module will now give the OpenGL framework as a dependency instead of the
nonexistent libGL.
Fix text being rendered with a vertical offset when the font's ascent doesn't match it's size.
Merge pull request #576 from binary1248/text_fix

Fix text being rendered with a vertical offset when the font's ascent doesn't match it's size.
Merge pull request #548 from jdpage/master

Adjust CMake module to provide correct deps on OSX
Improved resizing windows on OS X (close #474)

sf::Window::setSize will fire a resize event if the view could not be created at the requested size.
Improved sf::Http documentation concerning HTTPS