added -k parameter to sort by columns

tablizer.pod

@@ -20,6 +20,7 @@ tablizer - Manipulate tabular output of other programs
       -M, --markdown           Enable markdown table output
       -O, --orgtbl             Enable org-mode table output
       -s, --separator string   Custom field separator
+      -k, --sort-by int        Sort by column (default: 1)
       -v, --version            Print program version
 
 
@@ -78,6 +79,10 @@ The numbering can be suppressed by using the B<-n> option.
 By  default, if  a  B<pattern>  has been  speficied,  matches will  be
 highlighted. You can disable this behavior with the B<-N> option.
 
+Use the  B<-k> option to specify  by which column to  sort the tabular
+data (as in GNU sort(1)). The default sort column is the first one. To
+disable sorting at all, supply 0 (Zero) to -k.
+
 Finally the  B<-d> option  enables debugging  output which  is mostly
 usefull for the developer.