Refactor Package structure

This commit cleans up the package structure, to make two new top-level
packages `internal` (for internal-use packages) and `pkg` (for general
shared utility code).

pkg/fsx/type.go

@@ -0,0 +1,24 @@
+// Package fsx provides convenient abstractions to work with the filesystem.
+package fsx
+
+import (
+	"os"
+)
+
+// Exists checks if the given path exists
+func Exists(path string) bool {
+	_, err := os.Stat(path)
+	return err == nil
+}
+
+// IsDirectory checks if the provided path exists and is a directory
+func IsDirectory(path string) bool {
+	info, err := os.Stat(path)
+	return err == nil && info.Mode().IsDir()
+}
+
+// IsFile checks if the provided path exists and is a regular file
+func IsFile(path string) bool {
+	info, err := os.Stat(path)
+	return err == nil && info.Mode().IsRegular()
+}