Remove GUESS from Sci2 release in favor of GEPHI. Needs @katyb Approval.

[mginda]

Noted issues:
Mac OS X 10.10.5 (Yosemite) - when user tries to open a network with GUESS, a Java applet icon appears in the dock and then disappears, indicating that the tool crashes. The causes is likely a caused by issues with GUESS and Apple's Java implementation.