Resolve "add basic argument handling"

Closes #1 (closed)

project1/bin/main.ml

 open Dolmen
 module M = Dimacs.Make(Std.Loc)(Std.Term)(Std.Statement)
 
-let usage_msg = "project1 [--mode] [] ..."
+let usage_msg = "project1 [--mode] ... [files]"
 let input_files = ref []
 let mode = ref "xor"
 let anon_fun filename =