Extract helper methods for building config objects from dicts

Signed-off-by: Aanand Prasad <aanand.prasad@gmail.com>

tests/helpers.py

@@ -0,0 +1,16 @@
+from __future__ import absolute_import
+from __future__ import unicode_literals
+
+from compose.config.config import ConfigDetails
+from compose.config.config import ConfigFile
+from compose.config.config import load
+
+
+def build_config(contents, **kwargs):
+    return load(build_config_details(contents, **kwargs))
+
+
+def build_config_details(contents, working_dir='working_dir', filename='filename.yml'):
+    return ConfigDetails(
+        working_dir,
+        [ConfigFile(filename, contents)])