Hierarchy: remove snapshot_dir attribute and add boot_dir attribute

rbackup/hierarchy.py

@@ -67,6 +67,14 @@ class Hierarchy:
         date = datetime.datetime.utcnow().isoformat()
         return os.path.join(self.base_dir, date.replace(":", "-"))
 
+    @property
+    def boot_dir(self):
+        """Retrieve the /boot backup directory of this hierarchy.
+
+        :rtype: str
+        """
+        return os.path.join(self.curr_snapshot, "boot")
+
     @property
     def etc_dir(self):
         """Retrieve the /etc backup directory of this hierarchy.
@@ -83,14 +91,6 @@ class Hierarchy:
         """
         return os.path.join(self.curr_snapshot, "home")
 
-    @property
-    def snapshot_dir(self):
-        """Retrieve the snapshot directory of this hierarchy.
-
-        :rtype: str
-        """
-        return os.path.join(self.curr_snapshot, "snapshots")
-
     @property
     def root_home_dir(self):
         """Retrieve root's home directory of this hierarchy.