One panel by default is terminal is not wide enough

closes #182

src/bin/hexyl.rs

@@ -417,7 +417,10 @@ fn run() -> Result<()> {
     {
         max_panels_fn(terminal_width, base_digits, group_bytes.into())
     } else {
-        2
+        std::cmp::min(
+            2,
+            max_panels_fn(terminal_width, base_digits, group_bytes.into()),
+        )
     };
 
     let stdout = io::stdout();

tests/integration_tests.rs

@@ -565,7 +565,8 @@ mod base {
             .assert()
             .success()
             .pretty_stdout(
-                "  00110000 00110001 00110010 00110011 00110100 00110101 00110110 00110111   00111000 00111001 01100001 01100010 01100011 01100100 01100101 00001010  \n"
+                "  00110000 00110001 00110010 00110011 00110100 00110101 00110110 00110111  \n  \
+                   00111000 00111001 01100001 01100010 01100011 01100100 01100101 00001010  \n",
             );
     }
 }