Update _get_shell to work with Windows

- _get_shell assumed the parent process would always be the shell process, in Powershell the
  parent process is Python, with the grandparent being the shell
- Switched to walking the process tree so the same code path can be used in both places

thefuck/shells/__init__.py

@@ -18,11 +18,26 @@ shells = {'bash': Bash,
 
 
 def _get_shell():
-    try:
-        shell_name = Process(os.getpid()).parent().name()
-    except TypeError:
-        shell_name = Process(os.getpid()).parent.name
-    return shells.get(shell_name, Generic)()
+    proc = Process(os.getpid())
+
+    while (proc is not None):
+        name = None
+        try:
+            name = proc.name()
+        except TypeError:
+            name = proc.name
+
+        name = os.path.splitext(name)[0]
+
+        if name in shells:
+            return shells[name]()
+
+        try:
+            proc = proc.parent()
+        except TypeError:
+            proc = proc.parent
+
+    return Generic()
 
 
 shell = _get_shell()