Add a command that allows users to list collections on their account.
I'm thinking the command should be writeas blogs or writeas colls. With this, we should rename the writeas list command to writeas posts.
The list should include the collection alias (since users need this for other CLI commands) followed by the collection title (to help users remember what a collection is for). Ideally, these columns would be tab-separated to make things look nice, e.g:
matt Matt's blog notebook Notebook