add select output option -o

solves #7

mew.1

@@ -6,6 +6,8 @@ mew \- menu for wayland
 .RB [ \-beiv ]
 .RB [ \-l
 .IR lines ]
+.RB [ \-o
+.IR output ]
 .RB [ \-p
 .IR prompt ]
 .RB [ \-f
@@ -47,6 +49,9 @@ matches menu items case insensitively.
 .BI \-l " lines"
 lists item vertically, with the given number of lines.
 .TP
+.BI \-o " output"
+mew is displayed on the output name supplied.
+.TP
 .BI \-p " prompt"
 defines the prompt to be displayed to the left of the input field.
 .TP