added json logo for documentation.
added json logo for documentation.

tomgullo/rexster,alszeb/rexster,tomgullo/rexster,tomgullo/rexster,tomgullo/rexster,alszeb/rexster,alszeb/rexster,tingletech/rexster-tomcat,tingletech/rexster-tomcat,tingletech/rexster-tomcat,alszeb/rexster