Update starter code to match solution code

[MicFin]

The starter code in lib/deck.rb uses an instance variable when it should use a local variable.

  def draw
    @deck.shift
  end

  def shuffle
    @deck.shuffle!
    self
  end

Should be updated to

  def draw
    deck.shift
  end

  def shuffle
    deck.shuffle!
    self
  end

@jrhorn424 uses the attribute storage in solution code and deck in starter code to show redundancy of poor naming.

[jrhorn424]

Done as of https://github.com/ga-wdi-boston/ruby-enumerable-comparable/commit/a742b187564cbf79587b6c7e30758146e9cc000e