This is for consistency with `--include-drafts` (also plural).

To mirror all the other `hub release` commands, allow the user to delete
releases from the command line. The new subcommand takes only one
argument (the tag of the release being deleted).

Fixes #1326

Also add `--browse` functionality to `create` and `release` for parity
with `issue` and `pull-request`.

This is to free up `-c` for `--copy`.

The old `args.After("echo", ...)` approach won't cut it on Windows since
there is no `echo` executable. Thus, nothing was printed on Windows.

Instead, expand Args type with extra functionality that allows Go
callbacks after all commands in the chain have been run.

Also, the new `args.NoForward()` is now preferred to `os.Exit()` since
it's more descriptive and allows `defer` in the calling function.

Don't try to default `target_commitish` to the currently checked out
branch. Instead, keep the value blank unless explicitly provided. It
will default to the main branch on the server.

Since TAG is provided as argument, the user already knows the tag name
and there's no need to include it (rather clumsily) in the output.

Introduce a `console` package which encapsulates logic of printing out
to console. This provides flexibility of discarding output in tests.
It also allows us to unify format of printing to console (if we want to).

This fixes #801.

Print out aggregate error of asset upload instead of failing the whole upload process if one of them fails

Detect the asset info to upload via the `--attach` flag.

"The first block of the text"
becomes:
"The first block of text"

The definite article was not needed here.