feat(Flags): adds sugestions functionality

Author: kbknapp

src/app.rs

@@ -1835,14 +1835,26 @@ impl<'a, 'v, 'ab, 'u, 'h, 'ar> App<'a, 'v, 'ab, 'u, 'h, 'ar>{
             return None;
         }
 
-        let suffix = App::did_you_mean_suffix(arg, self.opts.values()
+        let mut suffix = App::did_you_mean_suffix(arg, self.opts.values()
                                              .filter_map(|v|
                                                 if let Some(ref l) = v.long {
                                                     Some(l)
                                                 } else {
                                                     None
                                                 }
                                               ), DidYouMeanMessageStyle::LongFlag);
+
+        // If it didn't find a good match for opts, try flags
+        if suffix.is_empty() {
+            suffix = App::did_you_mean_suffix(arg, self.flags.values()
+                                                 .filter_map(|v|
+                                                    if let Some(ref l) = v.long {
+                                                        Some(l)
+                                                    } else {
+                                                        None
+                                                    }
+                                                  ), DidYouMeanMessageStyle::LongFlag);
+        }
         self.report_error(format!("The argument --{} isn't valid{}", arg, suffix),
             true,
             true,