Rivers and Bridges map refactor (#103)

* Separated out rivers and bridges into its own file with three map variants

* fixing tags

* removed extra 4 starting positions from the medium map since it only supports 8 players

* update GetUnoccupiedPoints to consider hazards with a flag

* use new utility method to fine unoccupied points and enforce map sizes

* changed up casting to make IsAllowable() more usable

maps/hazards_internal_test.go

@@ -1,46 +0,0 @@
-package maps
-
-import (
-	"fmt"
-	"testing"
-
-	"github.com/BattlesnakeOfficial/rules"
-	"github.com/stretchr/testify/require"
-)
-
-func TestRiversAndBridgesSnakePlacement(t *testing.T) {
-	m := RiverAndBridgesHazardsMap{}
-	settings := rules.Settings{}
-
-	// check all the supported sizes
-	for _, size := range []int{11, 19, 25} {
-		initialState := rules.NewBoardState(size, size)
-		startPositions := riversAndBridgesStartPositions[rules.Point{X: size, Y: size}]
-		maxSnakes := len(startPositions)
-		for i := 0; i < maxSnakes; i++ {
-			initialState.Snakes = append(initialState.Snakes, rules.Snake{ID: fmt.Sprint(i), Body: []rules.Point{}})
-		}
-
-		nextState := rules.NewBoardState(size, size)
-		editor := NewBoardStateEditor(nextState)
-		err := m.SetupBoard(initialState, settings, editor)
-		require.NoError(t, err)
-		for _, s := range nextState.Snakes {
-			require.Len(t, s.Body, rules.SnakeStartSize, "Placed snakes should have the right length")
-			require.Equal(t, s.Health, rules.SnakeMaxHealth, "Placed snakes should have the right health")
-			require.NotEmpty(t, s.ID, "Snake ID shouldn't be empty (should get copied when placed)")
-
-			// Check that the snake is placed at one of the specified start positions
-			validStart := false
-			for _, q := range startPositions {
-				for i := 0; i < len(q); i++ {
-					if q[i].X == s.Body[0].X && q[i].Y == s.Body[0].Y {
-						validStart = true
-						break
-					}
-				}
-			}
-			require.True(t, validStart, "Snake must be placed in one of the specified start positions")
-		}
-	}
-}