Add pod repo remove [name] command

Deletes the repo named in the command.
Grouping all of the repo assertions together in command_spec
Update Changelog with pod repo remove change
separated spec:unit from spec:unit_quiet
Merge pull request #1493 from Kapin/master

Add pod repo remove [name] command
Merge pull request #1495 from CocoaPods/show_all_failures

separated spec:unit from spec:unit_quiet