Apply black formatter to code

[Travis] add a linting stage (via `black`)
[Travis] update as per code review
Remove "Lint" as separate stage; have `black` check the output rather
than run the re-formmater

jrnl/Entry.py

@@ -108,9 +108,7 @@ class Entry:
             return title
         else:
             return "{title}{sep}{body}\n".format(
-                title=title,
-                sep="\n" if has_body else "",
-                body=body if has_body else "",
+                title=title, sep="\n" if has_body else "", body=body if has_body else ""
             )
 
     def __repr__(self):