added additional specs for String#snakecase
added additional specs for String#snakecase

mpangrazzi/savon,savonrb/savon,enahum/savon,viniciusnz/savon,advishnuprasad/savon,payfriendz/savon,oafridi/savon,Eric-Guo/savon,zerobatu/savon,latortuga/savon,BlaneCordes/savon_vertex,SICSoftwareGmbH/savon,billr578/savon,rtrepo/savon