Append immediate execution to start action

This PR improves **Start** action for immediate execution and append **Schedule** action to avoid it.

Ref. threefunkymonkeys/crocodile#3
I like the idea of the rename and I do understand you can't break the interface.

When you create an alias, is intended to add readability to your code, but is not the best solution when you are building a shared interface for polymorphic objects.

The problem is when a user redefines the method or the alias. `Crocodile` will call one specific method (let's say `one_run_only`) but the _user_ overwrote `dismiss?` Look what happens.

```ruby
class User
  class << self
    def one_run_only
      false
    end

    alias :dismiss? :one_run_only
  end
end

class Emancu < User
  def self.dismiss?
    true
  end
end

Emancu.dismiss?
=> true
Emancu.one_run_only
=> false

########################

class Diego < User
  def self.one_run_only
    4
  end
end

Diego.one_run_only
=> 4
Diego.dismiss?
=> false
```

The user expects to run the job only once, but it will run for ever.

I can think only in a few solutions. Some sounds like hacks, but that's what you have to do when you want to support backward compatibility. At least for a few releases.

- Break compatibility to adopt a better name.
- Use instance variable instead of a method.
- Define and call both methods, warn to the use if uses the old method.
- Make the user call a method to set the `boolean` instead of redefining a method.

We can continue this discussion on IRC.