Switch from pathlib to pathlib2

The pathlib backport module is no longer maintained. The development
has moved to the pathlib2 module instead.

Quoting from the pathlib's README:
"Attention: this backport module isn't maintained anymore. If you want
to report issues or contribute patches, please consider the pathlib2
project instead."

thefuck/conf.py

@@ -1,7 +1,10 @@
 from imp import load_source
 import os
 import sys
-from pathlib import Path
+try:
+    from pathlib import Path
+except ImportError:
+    from pathlib2 import Path
 from six import text_type
 from . import const