Rename shared packages by day instead of vaguely by purpose.

2018/day07-2.go

@@ -3,7 +3,7 @@ package main
 import (
 	"fmt"
 
-	"internal/tree"
+	"internal/day07"
 	"internal/util"
 )
 
@@ -11,9 +11,9 @@ func main() {
 	data := util.ReadInput()
 
 	// Build a tree of dependencies.
-	root := tree.BuildDependencyTree(data)
+	root := day07.BuildDependencyTree(data)
 
 	// Build
-	time := tree.SimulateConstruction(root)
+	time := day07.SimulateConstruction(root)
 	fmt.Println(time)
 }