Deprecate AndJobs

[singularitti]

In PR #47 I created type AndJobs following the instructions from here to let

→(job1, job2, job3, job4)

can be written as

job1 → job2 → job3 → job4

However, why should I return AndJobs for job1 → job2? I can just return job2 as a final result. So it can be later chained with other jobs. It's just like

julia> →(a, b) = a - b
→ (generic function with 1 method)

julia> 1 → 2 → 3
2

julia> @which 1 → 2 → 3
→(a, b) in Main at REPL[1]:1

It calls that method recursively as long as both arguments are Ints.

[singularitti]

In commit 9c81a8d I changed returning AndJobs to just a Job. But this creates some problems: the association rule of → is different than I expected (method from here).

julia> "a → b → c → d" |> Meta.parse
:(a → (b → (c → d)))

As you can see, d will always be returned after that commit, so in the end, d will have a, b, and c as its dependencies, while a, b, and c has no dependency. That's not what I want. I want b has a, c has b, and d has c as a dependency. So I need to change → to another operator.

Every operator in this row has an association rule like →, so I cannot use this row.
The other row seems to be fine:

julia> "a ⊔ b ⊔  c" |> Meta.parse
:((a ⊔ b) ⊔ c)