added convinent to_s method for RelativeOperation

src/cligen/timeparse/relative_operation.cr

@@ -32,6 +32,14 @@ module CliGen::Timeparse
       raw.scan(CliGen::Regex::RELATIVE_OPERATION).map{|match| from_regex(match)}
     end
 
+    def to_s(io : IO)
+      io << to_s
+    end
+
+    def to_s
+      "%s%d %s" % [ @sign == -1 ? "-" : "+", @quantity, @unit.to_s.downcase ]
+    end
+
     # Just an initializer from a regex match. Only callable internally
     # so any operations must come from get_operations as that will handle
     # parsing it for the user