Fix property description

[yhoiseth]

routes() does not work, but routes does:

./manage.py shell
Python 3.7.0 (default, Aug 20 2018, 13:43:00) 
[GCC 6.3.0 20170516] on linux
Type "help", "copyright", "credits" or "license" for more information.
(InteractiveConsole)
>>> from platformshconfig import Config
>>> config = Config()
>>> config.routes()
Traceback (most recent call last):
  File "<console>", line 1, in <module>
TypeError: 'dict' object is not callable
>>> config.routes
{'https://www…

[chadwcarlson]

We have routes as a method in the other config-readers, and it looks like the inclusion of a @property decorator created this error. I have modified this in #13