Added rule for fixing Alt+Space character

Happens on the Mac a lot when typing a pipe character (Alt+7), and
keeping the Alt key pressed down for a bit too long, so instead of
Space, you're typing Alt+Space. This rule replaces the Alt+Space with a
simple Space character.

$ ps -ef | grep foo
-bash:  grep: command not found
$ fuck
ps -ef | grep foo

tests/rules/test_fix_alt_space.py

@@ -0,0 +1,18 @@
+# -*- encoding: utf-8 -*-
+
+
+from thefuck.types import Command
+from thefuck.rules.fix_alt_space import match, get_new_command
+
+
+def test_match():
+    """ The character before 'grep' is Alt+Space, which happens frequently on the Mac when typing
+        the pipe character (Alt+7), and holding the Alt key pressed for longer than necessary. """
+    assert match(Command(u'ps -ef | grep foo', '', u'-bash:  grep: command not found'), None)
+    assert not match(Command('ps -ef | grep foo', '', ''), None)
+    assert not match(Command('', '', ''), None)
+
+
+def test_get_new_command():
+    """ Replace the Alt+Space character by a simple space """
+    assert get_new_command(Command(u'ps -ef | grep foo', '', ''), None) == 'ps -ef | grep foo'