fixed links to 2012-2013 events, created HCC supercomputing sypmposium 2013 event page

content/events/2012/supercomputing_mini_workshop_2012.md

content/events/2013/HCC_Supercomputing_Symposium_2013.md

content/events/2013/hcc_condor_workshop_2013.md

content/events/2013/hcc_mpi_workshop_2013.md

content/events/2013/june_2013_osg_workshop.md

...nts/2013/supercomputing_mini_workshop_february_27_2013.md