Multiple security groups

 Added opportunity to specify more than one security groups
 and support of argparse for python2.7 and higher(optparse is deprecated since python2.7)
 
Examples : 
python >= 2.7 : 
          -g group1 group2 group3
        
python <= 2.6 :
          multiple security groups : -g 'group1,group2,group3'
          one  security group: -g group1 or -g 'group1'