Add Powershell as a supported shell

- There may be additional functionality to implement, but I've been
  running this way for a month with no known issues

tests/shells/test_powershell.py

@@ -0,0 +1,19 @@
+# -*- coding: utf-8 -*-
+
+import pytest
+from thefuck.shells import Powershell
+
+
+@pytest.mark.usefixtures('isfile', 'no_memoize', 'no_cache')
+class TestPowershell(object):
+    @pytest.fixture
+    def shell(self):
+        return Powershell()
+
+    def test_and_(self, shell):
+        assert shell.and_('ls', 'cd') == '(ls) -and (cd)'
+
+    def test_app_alias(self, shell):
+        assert 'function fuck' in shell.app_alias('fuck')
+        assert 'function FUCK' in shell.app_alias('FUCK')
+        assert 'thefuck' in shell.app_alias('fuck')

thefuck/shells/__init__.py

@@ -9,12 +9,14 @@ from .fish import Fish
 from .generic import Generic
 from .tcsh import Tcsh
 from .zsh import Zsh
+from .powershell import Powershell
 
 shells = {'bash': Bash,
           'fish': Fish,
           'zsh': Zsh,
           'csh': Tcsh,
-          'tcsh': Tcsh}
+          'tcsh': Tcsh,
+          'powershell': Powershell}
 
 
 def _get_shell():

thefuck/shells/powershell.py

@@ -0,0 +1,18 @@
+from .generic import Generic
+
+
+class Powershell(Generic):
+    def app_alias(self, fuck):
+        return 'function ' + fuck + ' { \n' \
+               '    $fuck = $(thefuck (Get-History -Count 1).CommandLine)\n' \
+               '    if (-not [string]::IsNullOrWhiteSpace($fuck)) {\n' \
+               '        if ($fuck.StartsWith("echo")) { $fuck = $fuck.Substring(5) }\n' \
+               '        else { iex "$fuck" }\n' \
+               '    }\n' \
+               '}\n'
+
+    def and_(self, *commands):
+        return u' -and '.join('({0})'.format(c) for c in commands)
+
+    def how_to_configure(self):
+        return 'iex "thefuck --alias"', '$profile'