Added support for return values from command callbacks.
Added printing to stderr to echo
Added result callbacks for groups.
Added imagepipe example.
Added a missing gitignore for imagepipe
Added imagepipe example to docs
Entering a context multiple times defers the cleanup.
Added a test for multi command entering.
Added support for passing through arguments to result callbacks
Preserve contexts around result callbacks and ensure that they are invoked without subcommands.
Added a test for pipelines
Added a changelog entry for open_file
Added open_file function.
Added test for open_file
Added pipeline documentation example
Added a chapter for parameter modifications
Added err to click echo docs
two -> three
first -> last