Use `cocoapods` as CLAide#Command.plugin_prefix

To create a CocoaPods subcommand plugin gem, add the file
`lib/cocoapods_plugin.rb` and load your subcommand implementation from there.

When the `pod` command runs, it will look for that file in your gem and load
it before parsing the command line.
Merge pull request #1563 from leshill/plugins

Use `cocoapods` as CLAide#Command.plugin_prefix
[Bundle] Update.
[Lib::Lint] Print the output of the project with --no-clean
[Lib::Lint] Inform users about the  option
[Validator] Validate vendored_libraries paths
[CHANGELOG] Updated for vendored libraries fix
[Validator] Validate vendored frameworks' paths
Merge pull request #1567 from Kapin/fix-vendored-lib

Fix linter not throwing errors when a vendored library's path is invalid
merge