Add call for FService::Base

[MatheusRich]

call should be the safe version of the current run (and future call!). call should work pretty much like run does, but it also catches any StandardError that may be raised in its body and encapsulates as a failure:

class Bomb < FService::Base
  def call # safe
    raise StandardError, 'BOOOM!'
  end
end

Bomb.call # remember that Bomb.call == Bomb.new.call
# => #<Failure:uu1D @type=:exception @error=#<StandardError: BOOOM!>>

With call! (with bang), we have the unsafe version:

class Bomb < FService::Base
  def call! # unsafe
    raise StandardError, 'BOOOM!'
  end
end

Bomb.call # remember that Bomb.call == Bomb.new.call
# => BOOOM! (StandardError)