Refactor exit_code implementation

cmd2.Cmd.cmdloop() now returns self.exit_code which should be an integer

Also:
- Refactored examples to call sys.exit(app.cmdloop()) in their __main__
- Running transcript tests now sets the exit_code accordingly based on success/failure
- Updated CHANGELOG
- Updated README
- Updated Sphinx docs
- Added unit test for case when transcript test fails

1 files changed, 3 insertions, 2 deletions

diff --git a/README.md b/README.md
index 86b9f8ad..b298a04c 100755
--- a/README.md
+++ b/README.md
@@ -227,6 +227,7 @@ A sample application for cmd2.
 """
 import argparse
 import random
+import sys
 import cmd2
 
 class CmdLineApp(cmd2.Cmd):
@@ -294,8 +295,8 @@ class CmdLineApp(cmd2.Cmd):
             self.poutput(' '.join(output))
 
 if __name__ == '__main__':
-    c = CmdLineApp()
-    c.cmdloop()
+    app = CmdLineApp()
+    sys.exit(app.cmdloop())
 ```
 
 The following is a sample session running example.py.