Enable internal_config values to work with floats

[gaieges]

If you add the following into the tests:

--- a/test.py
+++ b/test.py
@@ -26,7 +26,7 @@ def a_manifest(number_of_tasks=100,
                request_config=None,
                job_mode='batch',
                multi_challenge_manifests=None) -> basemodels.Manifest:
-    internal_config = {'exchange': {'a': 1, 'b': 'c'}}
+    internal_config = {'exchange': {'a': 1, 'b': 'c', 'd': .1}}
     model = {
         'requester_restricted_answer_set': {
             '0': {

It will break like so:

schematics.exceptions.DataError: {"internal_config": {"exchange": {"d": ["Couldn't interpret '1.1' as string."]}}}

Need to figure out how to make this work with floats