Added command line argument functionality

calcgc.py

 #!/usr/bin/env python
+import sys
 
 def calc_gc_perc(seq):
     atc,gcc = 0, 0
@@ -9,5 +10,6 @@ def calc_gc_perc(seq):
             gcc += 1
     return gcc * 100 / (gcc + atc)
 
-print "the sequence is 'CAGG', and has a GC% of {:.2f}".format( calc_gc_perc('CAGG') )
+inpseq = sys.argv[1]
+print "the sequence is 'CAGG', and has a GC% of {:.2f}".format( calc_gc_perc(inpseq) )