add pagination to GET /service/{}/job

accepts a page parameter to control what page of data

returns additional pagination fields in the response dict
* page_size: will always be 50. defined by Config.PAGE_SIZE
* total: the total amount of unpaginated records
* links: dict containing optionally prev, next, and last, links to
  other relevant pagination pages

also cleaned up some test imports

app/utils.py

@@ -4,7 +4,7 @@ from flask import url_for
 def pagination_links(pagination, endpoint, **kwargs):
     if 'page' in kwargs:
         kwargs.pop('page', None)
-    links = dict()
+    links = {}
     if pagination.has_prev:
         links['prev'] = url_for(endpoint, page=pagination.prev_num, **kwargs)
     if pagination.has_next: