Corrected typo in README.
Corrected typo in README.

mattoshry/SCION,mattoshry/SCION,mattoshry/SCION-CORE,mattoshry/SCION-CORE,mattoshry/SCION-CORE,jbeard4/SCION,jbeard4/SCION-CORE,mattoshry/SCION,mattoshry/SCION-CORE,jbeard4/SCION,mattoshry/SCION-CORE,jbeard4/SCION