Fix tests on py33, py34.

Author: jhgg

tests/core_language/test_parser.py

@@ -4,7 +4,7 @@
 from graphql.core.language.source import Source
 from graphql.core.language.parser import parse, Loc
 from graphql.core.language import ast
-from fixtures import KITCHEN_SINK
+from .fixtures import KITCHEN_SINK
 
 
 def test_parse_provides_useful_errors():

tests/core_language/test_printer.py

@@ -3,7 +3,7 @@
 from graphql.core.language.parser import parse
 from graphql.core.language.printer import print_ast
 from pytest import raises
-from fixtures import KITCHEN_SINK
+from .fixtures import KITCHEN_SINK
 
 
 def test_does_not_alter_ast():

tests/core_language/test_visitor.py

@@ -1,7 +1,7 @@
 from graphql.core.language.ast import Field, Name, SelectionSet
 from graphql.core.language.parser import parse
 from graphql.core.language.visitor import visit, Visitor, REMOVE, BREAK
-from fixtures import KITCHEN_SINK
+from .fixtures import KITCHEN_SINK
 
 
 def test_allows_for_editing_on_enter():