Handle multiple attributes

Handle multiple attributes on the same line : 

```
# example/decorator.attibs
test_decorator.fun_test_multiple_attr: fun_one, fun_two
test_decorator.TestMultipleAttr: class_one, class_two
test_decorator.TestMultipleAttr.test_one_and_two: meth_one, meth_two
```

```python
# example/decorator.py
class TestMultipleAttr:
    def test_one_and_two(self):
        print "Running test_one_and_two"


def fun_test_multiple_attr():
    print "Running fun_test_multiple_attr"
```

Output : 
```
(env2)./~pinocchio git:namedattr ❯❯❯ nosetests --decorator-file examples/test_decorator.attribs examples/test_decorator.py -a class_one,meth_two -s
Running test_one_and_two
.
----------------------------------------------------------------------
Ran 1 test in 0.000s

OK
(env2)./~pinocchio git:namedattr ❯❯❯ nosetests --decorator-file examples/test_decorator.attribs examples/test_decorator.py -a meth_one,meth_two -s
Running test_one_and_two
.
----------------------------------------------------------------------
Ran 1 test in 0.000s

OK
(env2)./~pinocchio git:namedattr ❯❯❯ nosetests --decorator-file examples/test_decorator.attribs examples/test_decorator.py -a fun_one,fun_two -s
Running fun_test_multiple_attr
.
----------------------------------------------------------------------
Ran 1 test in 0.000s

OK
```