added missing import
Most functions accepts lists as inputs

commit 81ce113cbac49448835c4c05f81a5da202a87899
Author: Nestor Arocha <nesaro@gmail.com>
Date:   Mon Feb 10 19:03:36 2014 +0000

    fixes new tests

commit 2e9c3cd4f54287fcc3f0718eca5ae7ee4c3a9ef7
Author: Nestor Arocha <nesaro@gmail.com>
Date:   Mon Feb 10 18:49:27 2014 +0000

    tests the new list inputs

commit 827fc277a30dd1329aa84a1b8bf71e51f620ffaa
Author: Nestor Arocha <nesaro@gmail.com>
Date:   Mon Feb 10 17:58:01 2014 +0000

    tests that Checker functions allow lists as input
Merge branch 'master' into 46-remove-symbol-reduction

Conflicts:
	pydsl/Parser/Backtracing.py
	tests/unit/test_Alphabet.py
	tests/unit/test_Extract.py
	tests/unit/test_Lexer.py