Suggest ag -Q when relevant

This detects when `ag` suggests the `-Q` option, and adds it.

tests/rules/test_ag_literal.py

@@ -0,0 +1,25 @@
+import pytest
+from thefuck.rules.ag_literal import match, get_new_command
+from tests.utils import Command
+
+stderr = ('ERR: Bad regex! pcre_compile() failed at position 1: missing )\n'
+          'If you meant to search for a literal string, run ag with -Q\n')
+
+matching_command = Command(script='ag \\(', stderr=stderr)
+
+@pytest.mark.parametrize('command', [
+    matching_command])
+def test_match(command):
+    assert match(matching_command)
+
+
+@pytest.mark.parametrize('command', [
+    Command(script='ag foo', stderr='')])
+def test_not_match(command):
+    assert not match(command)
+
+
+@pytest.mark.parametrize('command, new_command', [
+    (matching_command, 'ag -Q \\(')])
+def test_get_new_command(command, new_command):
+    assert get_new_command(command) == new_command