Fix a regression with Consecutives / OneOfASet

Two tests were failing:
```
FAILED edtf/parser/tests.py::test_edtf_examples[[1667, 1668, 1670..1672]-expected_tuple62] - AttributeError: 'list' object has no attribute 'expandtabs'
FAILED edtf/parser/tests.py::test_edtf_examples[{1667,1668, 1670..1672}-expected_tuple67] - AttributeError: 'list' object has no attribute 'expandtabs'
```

pyparsing.parse_string() was being passed a list by year somehow. Added year_basic for this use case (4 digit year without significant digits). If we need to support Consecutives with significant digits then this isn't a sufficient workaround.

edtf/parser/grammar.py

@@ -74,6 +74,8 @@
 negativeYear = NotAny(L("-0000")) + ("-" + positiveYear)
 
 year = Combine(positiveYear ^ negativeYear)("year") + Optional(significantDigits)
+# simple version for Consecutives
+year_basic = Combine(positiveYear ^ negativeYear)("year")
 
 yearMonth = year + "-" + month
 yearMonthDay = year + "-" + monthDay  # o hai iso date
@@ -271,7 +273,9 @@ def f(toks):
 consecutives = (
     (yearMonthDay("lower") + ".." + yearMonthDay("upper"))
     ^ (yearMonth("lower") + ".." + yearMonth("upper"))
-    ^ (year("lower") + ".." + year("upper"))
+    ^ (
+        year_basic("lower") + ".." + year_basic("upper")
+    )  # using year_basic because some tests were throwing `'list' object has no attribute 'expandtabs'` - somewhere, pyparsing.parse_string() was being passed a list
 )
 Consecutives.set_parser(consecutives)