Improve the texture module's documentation
Improve the texture module's documentation

sdotz/glium,bvssvni/glium,cpjreynolds/glium,caldwell/glium,binsoftware/glium,nicokoch/glium,rozaliev/glium,christopheraugustus/glium,TyOverby/glium,acolley/glium,tomaka/glium,carbidegames/glium,glium/glium,msiglreith/glium