fix: avoid panic generating default help msg if term width set to 0 d…

…ue to bug in textwrap 0.7.0

upgrade textwrap to 0.8.0 and add regression test

Cargo.toml

@@ -23,8 +23,8 @@ appveyor = { repository = "kbknapp/clap-rs" }
 bitflags              = "0.9"
 vec_map               = "0.8"
 unicode-width         = "0.1.4"
-unicode-segmentation  = "1.2.0" 
-textwrap              = "0.7.0"
+unicode-segmentation  = "1.2.0"
+textwrap              = "0.8.0"
 strsim    = { version = "0.6.0",  optional = true }
 ansi_term = { version = "0.9.0",  optional = true }
 term_size = { version = "0.3.0",  optional = true }

tests/help.rs

@@ -431,6 +431,15 @@ ARGS:
     <FIRST>...     First
     <SECOND>...    Second";
 
+static DEFAULT_HELP: &'static str = "ctest 
+
+USAGE:
+    ctest
+
+FLAGS:
+    -h, --help       Prints help information
+    -V, --version    Prints version information";
+
 #[test]
 fn help_short() {
     let m = App::new("test")
@@ -592,6 +601,12 @@ fn no_wrap_help() {
     assert!(test::compare_output(app, "ctest --help", MULTI_SC_HELP, false));
 }
 
+#[test]
+fn no_wrap_default_help() {
+    let app = App::new("ctest").set_term_width(0);
+    assert!(test::compare_output(app, "ctest --help", DEFAULT_HELP, false));
+}
+
 #[test]
 fn complex_subcommand_help_output() {
     let a = test::complex_app();